Don't need fancy measuring equipment. Carefully touch the exhaust pipe just before the muffler, then after. After is a lot cooler. So I revise my earlier statement.
I think a 3" exhaust to the mufflers w/ 2.5" tailpipes will be a tad faster than 3" tailpipes. Due to the cooler exhaust gasses getting a velocity increase from the smaller pipes.
With the added bonus of better fitment & overall quieter.
Your results may vary with like 610 cid engine vs a 360 cid.
Just my
When building a car you have to be a bit closer than... yep thats hotter than that... and temps come into play with making power
