@Chris is right and the YJ forums is likely a better bet but, from the sounds of it looks like a regear is in order. I had an 87 YJ with a 4 banger and 3.07's and it couldn't get out of its own way. The fastest it ever went was being flat towed behind my truck (not joking). Top speed under its own power was 60 mph.
It did have 33x12.5" tires though so that wasn't making things any better in my case.