Beginning of Sept I bought a new 2004 BMW 330Ci - performance package. Just about since new it has been idling like a tractor...took it to the dealer the first time....put it on the scope..."no fault found" and "all the performance package cars idle like that"...second time (today)...they reprogram the fuel injection....I get a mile from the dealer, pull up to a stoplight and its stumbling and chugging away again. Any ideas? I think it is a faulty fuel injector. Is there a way to isolate and just repalce the faulty one or do you have to pull them all?