D15b2 surging issue

I have beeen fighting a surging problem for a while now. I've read the other suggestions on this forum. Already checked the iacv, cleaned it out, with no effect. Changed the intake manifold, including all the sensors(TPS, IACV etc..) and vaccum lines. Still the same issue, surges while idling. The only thing I can see wrong is that the fan stays on all the time. I'm thinking there's a short or a bad relay, or possible bad ECT. The temperature is fine though, doesn't overheat and stays steady. Any suggetions would be helpful. thanks.

My fan is wired to stay on all the time and it's perfectly fine that way. Are you getting any codes or a CEL. If you have a check engine light come on, unbutton the carpet on the passenger floorboard under the dash and count the blinks on the ecu window. The ecu will blink once indicating it's working when you first turn the key. If it blinks any more, you have a code. To reset the ecu, pull the ecu fuse in the little plastic fuse box on the passenger side shock tower under the hood.

No ECU codes, forgot to mention that