If you look in the previous topics and posts here, you'll probably find out how wide it should be. I remember reading an article about what's the biggest wheel you can get in there, and I believe it was 20 inches, but I forgot how wide it could be. I'm sure it's more than 8 inches. The eibach springs are only going to lower front and back 1 inch. That is not a lot of lowering, but I've read that it's the only set of springs that will keep your wheels in proper alignment so that there won't be too much inside tire wear. So the Eibach springs and 18" wheels will be fine. Springs do sacrifice ride quality but I'm not sure how much. The Injen Intake should give you good sound, but It's not a cold air intake. That means your engine will be sucking in a lot of warm air. You also don't want to trust the dynos at the Injen website because the videos they show you have the hood open so that cooler air can get to the intake, but in real life you ain't driving with your hood open. Exhaust is good, but just remember to find out how it will sound like because exhausts are pretty expensive. Well sorry if I haven't answered all your questions, but there were no replies so I felt like doing one. Just use the search feature here.