When I start the car and let it warm up, everything is all good, runs well and boost is at ~5psi. After driving around for 20mins or so, it will start boosting to a max of about 3.5 or so.

Checked for leaks...what else cold be causing this, WG problem>?

edit: only noticed this issue after installing intercooler.

 

probably a boost leak that gets worse with heat. triple check for boost leaks, may be hard to find.

 

Ill check for leaks again when I get home thanks for the input.