Electrical wiring issue

Ok, some background on my problem.

Definitions so everybody knows what I'm talking bout!

Engine harness=connects to EGR, Evap, IAC, IAT, Injectors
Body Engine Harness= connects to fuse box, AC, Fans, power.

88 Cutlass Supreme with 3.1 Turbo 5 speed installed. I originally installed a 92+cutlass engine wiring harness that ran the turbo motor from my parts car. Old car was 92 Turbo swaped 5 spd.

I used my original 88 body Engine harness and modified to use with 5 spd.

With this setup I had issues with dummy lights on the dash staying on(battery light, ebrake light, 1 more, can't remember exactly)

Fast forward to this year. Swapped engine harness to a 90 TGP engine harness, no change. DOH!

Now comes today. I got a 88 Cutlass supreme, and used this engine wiring harness. I added the IAT sensor, as well as the Boost wastegate solenoid sensor.
-I also removed the 88 only oil pressure/fuel pump shut off switch that plugs into the lower intake by the coolant sensor.....left these pin outs on the black connecter by the ECM empty.
-Had a problem with injector connector, it broke, so I soldered a new one on matching wire colors, no problem.
-due to excessive rust, I could not get the power wires that connect from the alternator to the starter on the engine harness from the 88 parts car, so I cut the two wires and soldered onto the connectors from the old harness. I matched the thicker wire with thicker wire, and smaller wire, with smaller wire.

Now comes my problem!

Interior lights, and underhood light, only come on, once I try and start the car.

Car will start(woohoo) but dies immediatly as if I've turned off the car. Dash will remaind lit up as normal, everything else is normal. But the lights do not get power until I have the Key in start. I tried leaving the key in start, and it ran for 4-5 seconds and then I turned key back, and it quits.

Anybody got any ideas what's going on? I'm wondering if my solders were not good enough to support the power I need at the starter/alternator wires. Might need to re-run new wires...

Thank you for ANY help!!! I swear this car doesn't want to run for me!!