It will definatly help. I have BBK LT's 1 5/8ths into thier 2 1/2 H pipe into 2 chamber delta Flowmasters with no tailpipes. I did heads and all first also. The sound difference with longtubes alone make them worth it. It's not much louder cruising or at idel as it was with stock headers and stock H pipe, but when you open it up especailly above 4K rmp, wow. Yes you will gain some horsies, not to mention the mid range tq.