AWESOME GAINS! To the OP's post earlier - where the pipes neck down to about 2.5'-inches is the merge collectors ARH use. QTP is the only other major company I know of that use these collectors standard. These promote scavanging of the exhaust by keeping the velocity of the gases as high as possible. Kooks has something similar on many of their LTs, but they're not quite as good, from the looks of them (they have true high velocity merge collectors for an additional cost though for some models, last I checked). Anyhoo, these are great gains! I didn't really think they'd be this high, but considering the numbers - WOW! Has ARH mentioned if they are going to offer additional sizes and stepped primaries for the 5th Gen too?
05 Hummer H2 SUV on OEM Air Ride
Forged 11.1:1 408 LQ4 (K1 crank & rods; Mahle pistons)/CPP LS3 CNC heads/BTR Stage IV LS3 cam and valvetrain/home ported L92 intake manifold/ported 90mm TB/custom Volant CAI/mid-length headers/AFE dual 3" CB/Corvette Servo/el cheapo lift/Cognito UCAs/e'fan conversion/aluminum radiator/Moroso catchcan/HPTuners by me/LED exterior lighting/Pioneer AVH-5600BHS/Pioneer GM-9601/2-Pioneer TS-W310D4/Obcon Labyrinth dual-12 box/lots of other stuff