I recently had a service done on my 95 M3 at the local dealer. Along with the service, the valve cover gasket was replaced. After I got the car back, there was miss, or small backfire that started to occur at Idle. The car would drive fine, but at Idle it would miss. So I took the car back to the dealer and after numerous test, they concluded it was a problem with the air fuel sensor, and it was replaced. So I get the car back again, but it still has the same problem. I think they may have just increased the idle to compensate for the miss. Has anyone else experienced this problem, and if so, what was the cause? Thanks for any valuable information.