Misfire under load at partial throttle

Ok so this is what im dealing with.

I have a 93 integra RS that I pulled my old b17 from. I picked up another 93 RS with a b18a1 in it since it was a very clean shell. So I took the b18a1 and put it into my old car.

After fixing a ground issue I got her running pretty good. But I’m having a problem with this random misfire issue. Between 2200rpm-3000rpm the motor breaks up while under a load while giving it partial throttle. If you open it WOT it doesn’t seem to have this problem.

So for I have pulled the plugs and they look fine, changed plug wires, checked cap/rotor, and redid all my vacuum lines.

Today I drove it to put gas into it and afterward it seemed to be driving MUCH better. But after it sitting for a bit while I was working on it I took it for a ride after I was done and the misfire was there again.

When this b18a1 was in the original car it didn’t have this problem, which is why I was thinking it was problem with the old fuel.

Someone please help me fix this problem!

Yes the fuel or it could be the o2 sensor went bad do to the bad gas.

I think im going to try to drive it around some more and see if it helps. if not i’ll swap out the o2 next.

For future reference I swapped in a different o2 sensor and it now runs like a champ.

Thanks guys.