Stumbling after 4.0 head swap

[CoastieCJ]

Forgive the cross post from Jeepforums, but I figured this gang might have a little more experience with a build up like this:

I dropped a 4.0 (0630) head on my 258 that has a Hesco MPI kit. Before the swap, the engine ran fine, but I definitely felt it could use more power, hence the swap. Ever since then, I've had the worst time with it.

Upon startup while running open loop, it runs GREAT! It has a ton of power off the line and is very responsive. However, once it warms up (about 5 min) it starts exhibiting a bad stumble/misfire/backfire until it reaches 2100rpm. Then it will smooth out and run normally. But, if it is below 2100 and I give it any more than light throttle, it stumbles and/or misfires badly. If I disconnect the O2 or coolant sensor and force open loop, it won't have the low rpm problem, but it clearly isn't running great either.

The engine had a recent rebuild (20k ago on a 88 YJ block) It has the following mods: Crane cam (unknown model, supposed "dual pattern), new borla header, 99 intake, 63mm throttle body and adjustable fuel regulator (set at 44psi, but changing it doesn't affect the problem.)

I have done just about everything I can think of:
Replaced every major sensor (CPS,CKP,TPS,Coolant Temp, IAT, O2)
Distributor/wires/plugs (yes, indexed correctly)
Fuel Pump/Filter
Pulled the entire engine harness and checked for good grounds/continuity.

I just tested compression and found the following: 85,110,110,110,110,85. Those seem very low to me, especially for a recent rebuild. So, given that it had a new head gasket when I put the head on, is it possible that a cam failure on 1&6 could be causing the low compression #'s and the stumbling problem? Is it possible that the new head was decked (I bought it rebuilt 2nd hand, so no info) and that the pushrods are just slightly too long? Any other things that jump out to anyone?

Thanks!
-Lloyd