Flame arrestors, mesh, anything that causes backpressure.. unlike punching the baffles. Basically pulling the guts and modifying, cut/weld, as drill holes in the cones. If that helps in explaining, as long as it doesn't sound like sht and gives it a good note as ageing them.What do you mean by Drilled?
I'm running a thunderheader on 2 bikes,first is a 2002 dyna I've had for 10 years and 100k,chrome,no rust. 2nd is on my RGU,3 years,black,surface rust.thinking of sending it and the heat shields off for ceramic coating this winter.The dyna bracket did break,but it's does fine without the back half of the bracket.RGU Brackets have been fine.D&D Fatcat, I've read to many posts about Thunderheaders rusting and brackets breaking.