Fitech running fat

I’m not an expert but if it were me I’d temporarily run a return from the tbi and see what happens. Just takes a little time to remove the regulator guts, if it’s similar to Holley, and a return line to see. It can get frustrating. Sometimes we run into issues that “tech” hasn’t seen, or don’t want to work thru. In my case it wasn’t a psi issue but I believe a volume issue that couldn’t keep up with varying demands. Have you installed a new set of plugs also.