2.5L swap to a 2.2L
 

I recently swaped a 2.2L into a 92 shadow that used to have a 2.5L in it. I retained all the wiring, computer and throttle body from the 2.5L. The car idles at 2500-3000 rpm. I played with the timing and I don't think I have a vacum leak. My question is do I need to change the computer and/or throttle body?

Well, i may be wrong here but:

The computer is set for the 2.5, not the 2.2. so its sending out incorrect information. Has it not thrown a code?

The 2.5 SBEC is going to provide too much fuel for the smaller 2.2 displacement.

Too much fuel will not cause too high an idle. Too much air causes too high an idle. Your O2 sensor will control the fuel. Your throttle body may be open too much for the smaller engine. If you are positive there are no vacuum leaks the try resetting the Minimum Idle Air Flow. by adjusting the throttle blade opening. I have done swaps going from large to small and from small to large but have always used the correct throttle body.