GMC Repair: stalls under 800 rpms, fuel pressure regulator, intake manifold gasket

Question
hello, im working on a 1988 gmc pu 1500 5.7 tbi. the problem that i'm having is that the vehicle stalls under 800 rpm's  

Answer
Could be a vacuum leak somewhere in one of the vacuum lines.

Could be an intake manifold gasket leak.

could be a fuel pressure/volume problem.

Could be a fuel pressure regulator problem.

Could be ignition related.

There are just so many could be's that i would need to have access to the vehicle to find the cause.