Have you tried swapping another SR ECU into it? If droppin in the PFC made it run good then i would lean toward your ECU being bad.
I had a similar issue once, My ECU came unbolted from the chassis and it ran rich and misfired. I replaced the plugs No change, but as soon as i grounded the ECU back to the chassis it ran fine again.
P.S. Its spelled GReddy
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後輪駆動車１番
1989 Built SR GT2871R -363whp
1998 S14 W/RB25- 250ish (For Now)
1986 SR86 - 200ish
1990 R32 GTR - 320hp
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