This is an odd one.

I have a 94 GSR with a swapped b16. AFAIK, the swap was done well, by a shop. It runs great, no problems other than this. Plenty of power, hits VTEC hard.

Here's the problem:

At about 1400-1500 RPM, so under part throttle when warm, when controlled by the IACV when cold, or even if at that RPM in 5th gear, I get a sort of stutter/bog. It's only at this small RPM range and there are no other problems.

I was wondering why, when I got the car, the IACV was unhooked. Turns out this may be why - while cold, the RPMs tend to hover right around the range where it bogs, which makes the whole car shake and the RPMS jump up and down from 1200-1700 pretty violently.

Note again that this is ONLY at this RPM range.

Any ideas?