update
Heres an update to were I'm at. Removed and cleaned all battery terminals, added a ground wire from passenger side battery to engine block second post from firewall on passengers side, also moved the pcm grounds (20awg black/white and tan/white) to same stud also continued same wire to chassie ground for the hood and continued to drivers side battery and attached it to frame on drivers side. Ceaned ground straps on passenger side. Removed and cleaned the feed for fuse block in engine compartment, also pulled fuse block out and inspected the underside. Checked the PCM grounds at pcm connector to chassis and had about 2 ohms. Cleaned all connectors on firewall (scraped pins with small screw driver). I check the power a the PCM after it stalled and had 12v between orange wires and pcm ground also checked pink wires and pcm ground. Wiggled wires to ignition switch and still no luck. Also removed wiring harness from firewall and inspected. The truck will stall randomly sometime just cycling key and it will restart and run fine, other times the fuel pump relay and AC relays will just chatter (while they were chattering wiggled power, grounds etc. ) then just stop and every thing is fine. Also pulled the PCM and removed covers, visual inspection of board nothing appears burnt loose etc.. Not really sure what gmctd is calling the power block on firewall. I've yet to check out the ABS stupid thing idled over an hour and wouldn't fault. Open to any suggestions (minus setting the POS on fire as my wife suggested). Thanks (sorry so long winded)
97 GMC Suburban SLT, duals cat back, FSD cooler, 4L80E, 3.73 pretty much bone stock.