Originally Posted by wstar

Cleaning them is good maintenance. You can clean them while they're on the car, you just won't get the inside/rear bit quite as clean as you would off the car. Running a catch can helps with reducing the fouling on the back side as well. I've had mine off several times (and more than that). Removing and reinstalling them correctly doesn't hurt anything.

There's some basic "recalibration" stuff in the SM. Mostly you do these things after resetting the ECU, but it can't hurt after making intake/exhaust changes or cleaning out the TBs and cleaning the MAFs with MAF cleaner. It's all documented in Service Manual, section EC, around pages 18-20. Accel Pedal Release Position Learning, then Throttle Valve Closed Position Learning, and then Idle Air Volume Learning. If you use OBD-II stuff for a codescanner or Torque, etc, be sure to disconnect the OBD-II plug before you do these procedures or it will block them from working.