[kenmosher]

That's a lot of ground to cover with very little information... some things to look at:

1. Make SURE it's only running 15 PSI ... is the gauge accurate? Is the boost line feed to the gauge leaking (can cause erroneous low boost readings)? Too much boost and not enough fuel can result in lean popping and "cutting out"
2. Have you verified fuel pressure at idle (no vacuum line attached to regulator)? Should be 43-45 PSI. Also check with a pressure gauge under acceleration (should be boost PSI + base fuel pressure PSI... or about 60 PSI at 15 PSI boost). If not, it's fuel pump/line/filter related, most likely.
3. Have you verfied plugs and wires? Good wires? Proper plugs? Are they fouled or misgapped?
4. Coil Pack ... they can cause all sorts of missing etc. when they go bad
5. Check the battery cables carefully. Good CLEAN connection to battery? Is the positive cable touching the passenger's side header down on the frame where it passes near the header (you'd be surprised how often that happens)? Ground cable solid and clean to the bottom of the turbo mount?
6. Battery good? No weak/dead cells?
7. Wires tight on the nose of the start solenoid?
8. Wires on the back of the head (harness grounds) ... passengers side head (hard to see up by the firewall). Dirty/loose grounds can cause havoc
9. Wire on back of alternator clean and tight?