every now and then when i change car on single and multiplayer mode my new pedals (logitech formula force EX) dont work and slowly accelerate until max revs and i cant do anything about it except return to pits a few times.

Not a real big problem (yet) but its very annoying just wondering if anyone else has this?

or have i got a loose connection from my pedals to the wheel or something like that

Sounds weird to me, I have the same wheel. Does it happend randomly or just in several cars? What does the throttle bar tells? Have you tried calibrationg the wheel both in wheel's settings menu in Windows (or in profiler) and in game?