What gear is in that car?

Are you anywhere near redline in the traps and I'm guessing by the speed your at least a few 100 more rpm at each shift point and through the traps.

I used to turn my W2 like 7600 and above 4000 it felt like a nitrous shot, I imagine you benefit from jetting-up a bit for the new heads, unless maybe it was a little rich to start with on the big end and now it's just right.