Help fixing previous owners swap crap.

[Jahblah90]

I bought a 1987 Pontiac Firebird Formula that someone "swapped" a 350 into, but it doesn't run very well at all. The vehicle is currently running a quadrajet carburetor and has an HEI coil on cap mechanical and vacuum dizzy. It has some shorty headers with plugged AIR tubes, and a street dominator dual plane intake. I have noticed an abundance of wiring harness and unplugged connectors everywhere and part of the harness even goes into the passenger fender like my old TBI car harness did.

I just need to know how to find out what my vehicle's original fuel delivery type was so I know what direction to take for fixing it. If it WAS originally TBI, I want to go back to TBI. Same as TPI or carb.