I am sure that I have almost all the cars that you say not to buy, except for Saab. My question is: I have a Mercedes E55 AMG that has been modified with a smaller supercharger pulley and E63 mufflers. Do I need to have the computer reprogrammed? What should I look for in someone to reprogram the ECU?

yes, it would need reprogramming, good luck finding a guy who can mess with an AMG Merc. most guys won't touch em