Just got the 15,000 k service on my non-t xr6. After hitting the freeway and going over 100km/h I notice a pretty bad shudder in the front end either suspension or front wheels. Feels like the tyres are unbalanced but Im not sure. They did include the tyre rotation and balance in the service btw. I only notice the vibrations at speeds over 107km/h and am affraid of going any faster Any suggestions? Also Ive recently heard a croaking/almost grinding sound comming from somewhere in the car. At first I thought it was in the engine bay (I got new extractors and pipe) but not I think its more at the rear end. It only really happens when I turn sharply at slow speeds. Any ideas? Cheers. Also just off topic Ive wanted to lower and basically upgrade the suspension but am not sure what springs/shocks are the best, any help there would be sweet too. Cheers