I know KWs on E46s had a larger shock body and a helper spring which interfered with wider tires. Not sure if that is case on the E9X...I believe Porschefile had some fitment issue.
The NT01s make a nice coo-ing sound at speed. I think they are good for 1 second per minute improvement right out of the box. Do be aware that they don't make noise until you are already sliding. So you need to feel the car, not hear it. Otherwise you'll be in for an oh shit surprise As with R-Comps...they like more slip angle but are not as progressive when they give up. Try not to understeer a lot in them because you'll wear them out pretty fast.
I replaced a set of RS3s with my NT01s. My best lap on the RS3s at Texas World Speedway, a fast 2.9 mile course, was a 2:00:03. My best lap in the NT01s was a 2:00:02. But it was damp in some key places. I think the NT01s are good for an easy 1:56-1:57.
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