Just scrap the oem clutch. Its not a super expensive thing to get replaced with one that will last for the vehicles life. I've heard people say that when ever the factory clutch does anything weird its done.

 

I think the S2K makes a much better track car (not necessarily faster, but a better driver's car) because of the weight, cost to run, and the RWD.

The steering on the two cars is very similar. Very quick ratio. The S2K is a 2 door go-kart and the Evo is a grocery-getting go-kart. They make a great pair. Both very fun, very reliable, and very cheap!

 

I know what you're talking about the car vibrating at high speeds. I didn't know what to think so I asked the dealer. Their stupid answer was "drive slower". On mine it used to happen from 90+ - 100. That's gone now I think it was just the tires from what I hear they don't balance very well.