That sensor, the IAVC, is on the back of the Intake manifold. You can swap it out with your previous motor(Si, dx, whatever).
First I'd try resetting the ECU by pulling the Hazard fuse in the engine bay box for 10-15 seconds.
It may possibly also be your distrubutor. Does your tach bounce around alot at WOT or high RPM's? If so, it could be your ignitor. I've had to replace my distributor three times, everything else works fine though.