I've been driving around with 5.8 on my STi. It's fine around town. I drove mine and a stock STi (mine had 4.0 stock) and the biggest difference was that mine turned in faster and required less wheel input. Of course mine also had a heck of a lot more camber and some toe out where his was aligned by the dealer (which probably means 0 toe and 0 camber). I'd be nervous about running more than 8 degrees of caster, but 6 doesn't seem to be excessive.