I have a set of aftermarket fender braces on my STI. I did notice an improvement in steering response, but I also have poly steering rack bushings. I haven't noticed any change in ride quality though. I've let a few other WRX & STI owners drive mine, and they all noticed a difference from their own cars. They are good stuff, and probably would make an improvment on a S30. Then again, I'm not an engineer.