My idle fluctuates up and own by a couple hundred RPM on my fuel-injected engine.

From RPRWiki

Your Throttle Position Sensor (TPS) has gone bad. This is the portion of the throttle body that tells the ECU how far open the choke plate is. Normally, if the TPS goes bad you must replace the whole throttle body because the TPS is attached with slot-less screws. But, you can cut slots into the TPS screws with a file or a Dremel tool and unscrew the TPS. Swap in a junkyard TPS and that should fix your problem.