2.5 to 3.0 Exhaust

I have a Hi-Compression (11/1) ~400hp 367, running a 4-speed, TTIs,and dual 3s. I ran it with the H-pipe for 4 years or more, but had to ditch it when I installed a GVod.
I immediately noticed a pretty good loss of bottom-end torque. I worked on my tune all that summer, but never got it all back. It took some 10 to 16% more low gear to get the low-rpm (sub-2400rpm or so) performance back, which as a streeter with a 4-speed and 3.55s, was very important to me.
Point being, don't underestimate the value of the H.