On cold starts it starts up fine, but will not idle on it's own unless I hold the revs up a little for about 30 seconds, but then when I put it in gear to start going it acts like it wants to bog down and even sounds like it wants to backfire. If I have the RPM's up higher than normal while taking off it does not do it. When the car is up to temperature every so often the RPM's drop down close to 500 RPM but never any lower. A quick rev will get it idling back to normal. The previous owner never mentioned the engine having a cam, but it does sound like it. I also know that having a vacuum leak can cause the engine to sound like it has a cam. I'm new to the Mustang world, and I haven't been around many, but would having a cam cause the engine to rock at idle? Because mine does. Sitting in the car you can feel the car rocking side to side. Someone told me it sounds like it has a B cam in it. I know videos don't give you the best idea of what something sounds like, but my car doesn't sound like any Mustang on Youtube with a B cam in it. I have checked for vacuum leaks and haven't found any. I have cleaned the TB and IAC, then I replaced the IAC because it would not come all the way clean. Also, when I replaced the IAC about a week after cleaning it I noticed a little bit of oil coming out of the holes that wasn't there when I took it off to clean it. Could oil be causing this if it's just sitting in there for a long period of time? Should I keep going with checking for vacuum leaks?? The codes I have are for the 02 sensors, some fuel circuit code, engine coolant temp and one for not controlling idle at high rpm's.