Hi out there!
I know someone will have the answer to this problem.

My Min was running poorly, even though she just has 27k miles. I took her to mechanic and after inspection, he said the spark plugs had significant buildup - odd where car is designed to go 50k before tune-up. I told him to change plugs and put in a new air filter. He did. When I got the car back, she still ran like an old lady. I can't figure out what else to do for her.

In old cars, you might up the timing, but I don't think they do that to fuel injection cars. Any ideas?

Thanks.
2005 Mini Cooper S.

 

Are you completely out of the 4 year warranty period? If not, take it to the dealer.

If so..

Is the car running rich? Can you see a lot of black buildup on your tailpipes? Check your O2 sensors. They can be failing and affecting your performance even if they haven't thrown a code.