SR redtop pulling code 55?

[SoguRacing]

I'm not sure what this code mean. My car has a rough idle and this is the only code i'm able to pull. i've tried multiple ecu's, maf's, igniters, changed spark plugs, timing is correct, changed spark plugs, swapped around the coils, checked for injector leaks and all seems well. I dont understand my rough idle. it also hesitates when cruising. pulled code 55. some input please.

1991 rebuilt s13 sr redtop with #62 ecu.

[reactor]

Code 55 means No Malfunction Detected

[SoguRacing]

ok. my car idles off beat and has a slight hesitation under load.

[Homer_Simpson]

Done anything to it lately? Replaced any sensor?

[SoguRacing]

i've converted it completely back to a stock sr. no more upgrades. completely stock. i've let the car sit with the battery unplugged over night to reset the ecu and it still doesn't run any better. i have literally no clue what the problem could be.

[slider2828]

Sogu, what does running like crap mean? Idling or what? Most likely its vacuum related...

[singlecamslam]

IACV valve? Mine idles like crap because of it.