Hi everyone, I'm having a little bit of trouble with my 01 Mustang Gt. It's mainly stock except for exhaust, cai, and a typhoon intake manifold that was installed by the last owner. I noticed a few weeks ago while driving on the highway my rpm's would drop a couple hundred then go back up a couple hundred rpm's. It does this around town as well. I decided to clean out my throttle body and maf with maf cleaner. Then the next day my engine light turns on for a P1506 (idle air control over speed error) and I notice my idle in Park is a little high, it's at 1000-1200 rpm. From doing research online I decided to clean out the idle air control valve. That didn't fix it. The I replaced the pvc and also replaced all of the hoses incase there were any cracks. That didn't fix it. I went back and cleaned the throttle body and maf again. Didn't fix it. Replaced the iac valve with one from Autozone. Didn't fix it. I'm also clearing the engine code after I try something new, then I drive the car for about 10 mins and then the engine light comes back up. I'm not sure what else to look for. Anyone have any ideas? Thanks!