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?
"...What IS true: We anticipated that this would happen - we are never finished - and yes, Ford DOES deserve to win now and then. To think that GM can come out with a car to make ford throw in the towel is simply foolhardy..." - fbodfather