Additionally, what I am looking to gain from a tuner is somewhat common: more torque, horsepower, etc. Maybe increased top speed.

 

I have a wedge style screaming eagle air cleaner. Not open all around. No issues riding in south Louisiana down pours.

I see you are talking after market tuner. I have no dyno results to prove it but if its HP and torque you are wanting you might entertain going stage 2. After market cam, tuner and a few other products. This will easily get you into the +100 HP and depending in cam really good torque you will feel along with throttle response.

Also a canned or auto tune will not get you the results of a good dyno tune.

 

With the HD tuner you will gain a little but its not going to be anything big because its an EPA restricted device. In my talks with DynoJet about my 24 RG, they told me that the stock air cleaners are basically simple forms of a high flow air cleaner. I know you want to maintain the warranty but you'd see much better gains with an aftermarket tuner. Fuelmoto published dyno charts of a bone stock 24 RG 117 with an enhanced tune with Power Vision tuner and it made good improvement over stock. They also have one with just a 2-1 exhaust and PV tuner and that made even better numbers without a cam. Both Dynojet and fuelmoto told me these gen 2 M8's can make good power but are limited by the tune and fuelmoto's dyno charts with the power vision tuner proves that. Now to answer your question, no, you dont need an air cleaner but you wont see or feel the gains you want without an air cleaner and a better tuner. Welcome to the forum

 

On air cleaners I keep the factory air housing and changed to the SE Hi Flow filter from the factory paper filter. But same factory housing as standard. I been questioning if it really is a difference in the filters
I also have the SE Pro tuner and the dealerships left it plugged into my bike harnesse because I added Bassani 2-1 Comp pipes

 

The fist thing I did like many is change the air cleaner to a higher flow ( also did a stage 2 cam day one on my new M8 ) but every time a see a rain cloud I question my choice and not just me, Harley too as just one example that stock OVAL 114 intake is not exactly water proof and IMO it should be. Even my old school EVO Carb Super E S&S teardrop cover let plenty of air in and never required a rain sock...
Also you can buy higher flow filters for stock housing. I use a Arlen Ness oval Big Sucker in my SE oval filter housing as just one example but I had to aslo buy the larger than stock rain sock.
I'm a fan of that filter, built well and sucks some air and being black does not fade like my K&N red filter did.
I think you got options OP if you dig around a bit as you may can kep the same filter housing stock look but flow more air.
Also, IMO life is too short NOT to install a cam sooner than later. The sound alone is worth it for me but I ride a bike hard and prefer the added pull down low and the sound of a M8 needs it IMO as I came from a cammed EVO...
A stock M8 sounds like a UPS truck to my ear...

 

Steve Cole (of TTS) has done extensive testing of different air cleaner assemblies for the M8's and found that the M8 is very responsive to air cleaner changes, moreso that just changing mufflers. You can stay warranty compliant and get large gains with the right combination of air cleaner, the Pro Street Tuner and an EPA legal 2 into 1 exhaust system. Yes, if you don't care about your warranty there are even larger gains to be had. Once you start adding a cam and/ or compression to the mix, even larger gains can be had.

 

My 2 cents is that if you are that concerned about the warrenty, then keep it mostly stock until your warrenty is done. Then look at enhancements that are not SE/OEM based. They are far too limited by the EPA to make it worth your time and expense. Your money will go a lot further using non SE/OEM components, including the tuner. Talk to Fuel Moto to start the process of deciding what you want the bike to do.

 

I know some or perhaps many will agree with the above statement and "keep it stock" until warranty is over However, I disagree with the above advice ( for me personally ) and this is why.

#1 IMO and for ME personally Life is too short for stock and life is too short holding off 2-years until warranty is over to do fun stuff to my bike. I don't know what tomorrow holds much less 2 years from now. I may not be riding in 2 years?

I have used 3rd party cams and such on my older bikes but right now, in the area I live, I have 3 Harley dealers with-in 2 hours of my home and none will do 3rd party tunes. Yes I could have voided the warranty but I'm glad I had a Harley SE warranty friendly option, yes its $$ but was worth it to me even if I redo it now the warranty is up or I may do nothing as I am happy with my bike.

I have NO local 3rd party tuners with dyno I trust so the idea I can gain performance via my dealer is something I decided to embrace.

As far as "not worth my time or expense" one never knows the size of someones pockets and what he values and is willing to spend his money on.

I understand SE is limited over 3rd party but as I pulled out my dealer day one with 16 miles on my bike, Stage 2 installed I had a smile from ear to ear and about a week later as I pull through my local Indian dealers parking lot and a customer passes in front of me and shouted "nice sounding cam" I was thrilled I paid to have a warranty friendly Stage 2 done on my first day of new bike ownership!

Now 2 years later, I have one month left on my new bike warranty.
Now 2 years later, I am at a point that I am considering a few options...

#1 keep my bike as it is and do nothing but ride it ( I love it and all that I have done to it ).
#2 travel or ship my bike to a place such as Moonshine for a 3rd party mild or wild build.
#3 at least go 3rd party tuner as soon as warranty is up in s month.
#4 Sell the bike, or keep the bike for the wife and ALSO buy a new Road Glide CVO ST.

Regardless whatever I do, I have zero regrets doing a warranty friendly SE stage 2 and so glad I did as it made me enjoy my new motorcycle more than stock these last 2 years. Coming from a EVO the sound alone of a cam in a M8 was worth the price of admission.

 

Hey, the op said that he wanted to maintain the warranty. I suggested (to the OP) that given the expense and limited performance improvements, SE, OEM isn't worth it. If you choose to spend more, and get less, go for it.

 

To the O.P., if you are desperate to spend money. Get an air cleaner, to go with your slip on, have the dealer download a canned tune, and you'll be set.

 

I too just added the hi flow filter inside the stock housing….along with a Khrome Werks dominator full exhaust and the SE tuner. Seasoned tech at HD when I bought the bike said that stock intake on these motors with just the upgraded filter only will allow more than enough air to get you through stage 2 and maybe beyond depending on choices. Right now the motor does everything I need at the moment, but a cam will be added soon enough.
Buddy of mine has stock headers, tab slip-ons, and just recently added the tuner and SE snorkel type intake. He noticed huge improvement doing so, but I still believe it will breathe better if you put headers on.

 

I too just added the hi flow filter inside the stock housing….along with a Khrome Werks dominator full exhaust and the SE tuner. Seasoned tech at HD when I bought the bike said that stock intake on these motors with just the upgraded filter only will allow more than enough air to get you through stage 2 and maybe beyond depending on choices. Right now the motor does everything I need at the moment, but a cam will be added soon enough.
Buddy of mine has stock headers, tab slip-ons, and just recently added the tuner and SE snorkel type intake. He noticed huge improvement doing so, but I still believe it will breathe better if you put headers on.

I went with a Bassani no cat header with my Rinehart DBX45 as it was about 1/2 the $ of other options at the time.

I live on the Coast in the deep South and not having the cat helps as me or my passenger are NOT roasting even in heavy traffic in the Summer. I do have the oil cooler fan that may or may not help with that?