Hey guys I have a 99 civic si (b16a2). Mods include full greddy turbo kit, test pipe, exhaust, fpr, and the rest is stock.
I noticed that when I hold the motor at a constant rev, between 2k-4k it drops about 300rpms then comes back up and keeps doing it. When I hold it constantly under 2k or above 4k it does not do it.
The only code the motor is throwing is from the o2 sensor on the cat (i'm running a test pipe).
Any help is appreciated.

 

if you dont want it to throw the 02 sensor code.. take the o2 out of the exhaust and zip tie it under the car somewhere.. it should fix it just fine