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clear the Computer and do another diagnostic.
either your fuel pump either 2 of them Inertia(inside tank) and high pressure(External)is on its way out.
fuel filter blocked??.....
it does sound like it is a Crank angle Sensor (CAS) problem or the Air Flow Meter(AFM).. thats what they cause when not running correctly.
u say u have swapped the afm was it a good working one???? Backfires can cause the hot wire in the AFM to blow out and destroy the AFM..
was the CAS(inside Dizzy) a good one as well??? (Where these from a wreckers? could be damaged already)
also check all your vacuum lines as well as your intake piping has no leaks between AFM and throttlebody this will cause car to run ****.
Let us know..... it does not sound like a huge problem... i would say nearly all Rb30 owners have had this problem before as the engines are 20+ years old now.
Another could be the Throttle Position Sensor(TPS) or AAC Valve located on Plenum..
Goodluck