What is the recommended fuel pressure for a 1986 tpi unit? And what kind of presure does a stock gm fuel mechanical pump produce?

Generically the TPI should have about 35 psi at an idle. If the vacuum line to the regulator is removed, it should increase the pressure about 10 psi to 45. If you dead head the pump or pinch the return line, the pressure should exceed 60 psi.

Mechanical carburetor pumps usually only make about 6-8 psi

HTH