harshness can easily be the tire itself - a soft sidewall tire will help a LOT - i changed from the bridgestone S0-3 to the yokahama AD08 and the car immediately got civilized, whereas before every bump jarred you - too much pressure will also cause that - start at 36 cold and see where it is in temp and wear
wandering or tramlining can also be the tire - it can also be the toe set - often shops set too much toe in the car, and it always leads to this
as for the rest, if you aren't racing, it really won't make all that much of a difference in anything, though you will probably notice longer braking distances as well as the reduced acceleration, and i would be more concerned about that one than the acceleration - once you get used to it though, it will be fine
94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating
www.968forums.com
"It isn't nearly as expensive to do it right as it is to do it wrong."
