For your fuel cut issues,
After you have double checked for boost leaks (build yourself a boost leak tester or coupler with a nipple to go over the turbo is a good way, then cap the other end before the throttle body.) make sure your wastegate actuator is not seized or locked up.
Mine did this a few years back and I could figure out how to get rid of my fuel cut and my almost 22 psi spikes:aigo: (regardless of where I set my boost controller) until I replaced it. So double check that as that will causes unlimited spool and a blown turbo, amongst other problems.
Good Luck!