What type of performance will I get from a shark injector hp, etc? Can I expect much from it? Also, in regards to a complete tune-up on the vehicle what do I need to do? Can I do some of the tune-up myself? What the best spark plug for my car, oil? What type of horsepower does my 528 have? Any other performance upgrade that I can do, please let me know.

Would like to replace my factory rims, I currently have 17 inches M5 style rims. What is the highest size that I can get without compromising ride, etc? Any rim/tires web store recommendation PLEASE?

Lastly, I live in the Chicago, Il. Where can I find a reputable certified bmw mechanic without having to go to the dealer?

Thanks to all for all the help!