its the same as slp and stuff. I would go to a muffler shop have them duplicate the elbow that goes onto the muffler and have them make a straight pipe axle back. 3 of my friends have done that here at a local muffler shop. 150 bucks including 4" tips and they sound exactly the same as boom tubes and slps.
Boom tubes sound alittle different then straight pipes like SLP, they have alittle insulation to change the sound some. I think anything sounds good with the prochamber and you may loose alittle tq, but you'll hardly notice.
IMO the boomtubes have a better sound than straight pipe, they have a baffle inside that smooths out the rough edge a bit, i dont think its quite as loud as LM or straight pipe but has a low rumble, more refined, and the 4" stainless pipe looks good too.
heres a couple pics, you can see the baffles inside