I'm just getting caught up on this thread. From what I gather, you say you ONLY have 90psi compression AFTER the new top end was installed?? If that is correct, that IS your issue, not something else mechanical.
@OLD CT had mentioned this earlier and it seems you've glazed over that reply. All of the CT engines I've built will make 150 to 180psi right after assembly....before I even fire them! Like others said, a picture says 1000 words. There are alot of JUNK incorrect cheap top end kits advertised and sold, and if you have the wrong parts installed, you have the wrong parts, period. Until you confirm you have the right head and piston configuration you're chasing a ghost looking for a problem that doesn't exist, or looking in the wrong areas for another problem. When really the issue has been staring you in the face the whole time, one that may have been created unknowingly by yourself because your bought something that was falsely advertised by a vender strickly concerned about money. Honest mistakes happen, you trusted what you read, doesn't mean it's true though. Everyone here WILL help you, we just NEED more info as we are not there and did not build your motor. You're in the right place for help, don't give up!