No hard numbers to report - really not a numbers guy anyway.
What I can say is my 1300F EGT limit is much harder to hit and takes longer to get to. They also drop much quicker and go lower than at idle than with the previous exhaust muffler (with the "stealth" 1-1/2" core).
Having the lift pump ON made the flat spot move up higher in the RPM range but it's still there. This proves that the pump is a fuel restriction (even when it's on) which seems a bit odd. However I really have to be hammering on it to feel it, and it's a good regulator valve till I get a new transmission. I could route a by-pass with a ball-valve and a few "T's" I suppose, and just use the lift pump for the odd time I run it dry.
After three years of weekends with virtually every part of this engine in my hands, I really can
FEEL it's relief with the 2-1/2" exhaust. The entire vehicle just seems happier - as does the driver