According to the TBI brain trust, it is supposed to be between 9 and 14 psi, but they say 10 minimum, or you can get lean backfires back out the tbi, and rough running under load. Two issues I am experiencing. It may well be the distributor as well. But I like to know instead of shotgunning parts. Compression cold is 160 to 170 on all 8 cylinders. It is an '88. Timing is set to zero with that wire disconnected.
I have replaced cap and rotor, plugs and wires as some of the boots broke when I pulled the plugs for the compression test. Plugs looked ok, but I had new ones, so. I do get a good cone of fuel on the throttle plate, and it idles pretty good at 650-675 rpm when warm. Want to like the truck, just haven't warmed up to it yet.