I just had my 30K service done which included spark plugs. My car now feels less powerful especially at the top of 2nd and 3rd gear. I almost feel like the turbo's are not kicking in like before the service. The car is definitely not as responsive at top rpm's. I have a feeling the previous owner had a computer upgrade on the car and maybe BMW wiped it out when they did the service. Wondering if anyone else has had a likewise problem. Of course, BMW says all is fine...thx!