On the Subie WRX, I had intermittent slow idle, and was advised that maybe just cleaning it would solve the problem? Didn't seem to do the job, even with new gasket and O ring.

Not sure who is correct, but my mechanic told me that a scan tool would have to be hooked up to check the factory settings and adjust the IACV with the slots, but a member of the subie club said that it is controlled by the ECU. I'm not sure who is correct??

http://forums.nasioc.com/forums/showthread.php?t=1704762