I have been playing a LOT of GT4. I won a BMW 2002 Tii by winning the 120i one-make race. I modded it completely out and it rules! I beat a Ford GT on the Tsubuka wet course with it. Special Condition events are the best!
There are very few non-race cars that the 2002 can't beat. It really surprised me. It's very light when fully lightened. I haven't modded out my M3 GTR yet but it's pretty fast as is.