Mattax said

The X-pipe may or may not help. There's diffent flavors and diameters. Depending on where in the exhaust it is located it may help at certain rpms, and it might help share or may just be a disruption in the flow.
Off the top of my head, I know the placement for an H pipe using pipemax usually works out to roughly 20" after the end of primaries.
I would not worry about 2 1/8" tailpipe after the muffler if that is the only damage. If its a sharp turn right at the muffler or crushed right there, then get it redone.
Got two things going on.
One the exhaust is cooling off as it progresses through the system. Mufflers abosrb a fair amount of energy themselves (turns into heat). With the drop in exhaust density a smaller diameter is fine.
Second, at low rpm the smaller tailpipes will keep velocity up. The better the velocity, the less atmosmopheric pressure can effect the exhaust pulses.

The step headers might help with reversion at low rpm, and they might help in the upper rpms but no guarentees.
You could run the numbers in pipemax for a ballpark estimate.

Click to expand...

MopaR&D said

I'm guessing you have the exhaust necking down from 3" to 2.5" right after the collectors? Try this... run 3" pipe off the collectors at least 2 feet back THEN have it go down to 2.5".

Having the diameter change right off the collectors kills the mid-range scavenging effect of the secondary portion of the headers. From where the primaries meet at the front of the collector it needs to be consistent diameter at least a few feet back.

This is also the main reason why running open headers with no collector extensions loses power, same effect.

Click to expand...

crackedback said

Any claims that one set up is better than another, X, H, no crossover is ALL combo dependent.

What works on one build may not work as well on a different set up when it comes to exhaust.

Click to expand...