Welcome! Prepare to get inundated by answers. Hit the search button for pipes, A/C, etc., and you'll get opinions. First off, basic mods will be, among other things, "do we chrome it out or black it out?" No right or wrong, but doing either will dramatically change the looks.
I use the HD Heavy Breather A/C and Vance & Hines Monster Round Slip Ons. PLENTY of "beef", moderate volume. Need more? Go to V & H Hi-Outputs, Reinharts, (or plenty others) or the CFR slip ons. Real CFRs or CFR Knock-offs you ask? Good question! Big difference in $$$, some difference in sound and quality.
I love the Battistinis stuff also, without going to the extreme. Biggest complaint with V & H slip ons and HD Heavy Breather is that "everybody has them...I want my scoot to be different".
Still, I haven't seen a scoot set up exactly as mine. However, with your ability to MAKE parts, the sky is the limit! To each his own: