My Ford bf idles rough and varies in rpm, but if you turn it off and then on it works fine, I start it up and it sits on 2000rpm and then drops its way down to 1500rpm and can drive around like that and put it netural and it holds at 1500rpm.

You start the car and it runs normal rpms. Sometimes it will happen once or twice, meaning it will run normal three times in an row and then it will have this problem. I have checked the Inlet manifold gasket and TPS,throttle body and they are good.