What hurts the 1 7/8" is they typically have the too small 3" collector. I modify the hooker 1 7/8" to take a 3 1/2" collector because with an auto the overall torque in the real world "2500-5000" street powerband is better, even if it starts to give up a little HP above 5000. Torque is momentum and momentum is 90% of optimizing your ET with a true street set-up that's not running drag slicks and a full race converter.
with a full exhaust system it's difficult to prove the larger 2" pipes have much (if anything) to do with any ET gains, But on a race motor (that's never running below peak torque RPM the whole run) a 2" is a better investment. The 1 7/8 will be more forgiving of a too tight converter or a higher gear, plus your roll-on part throttle (again real world) torque you actually use every day is better.
Guys that say "no you have to have a 2" or bigger" might take some lessons from the F.A.S.T. guys...the guys now running high 9's on factory manifolds and 2 1/2" exhausts
Optimum tube lengths and diameters that formulate for a given HP target on a race motor or running unmuffled on an engine dyno can seldom duplicate their full benefits when installed in a street car running a full exhaust system, the reason is you simply cant launch/hook/drive it on the street very often the way you would on the track.
