I just purchased a low mileage well maintained G35 that has a vortech supercharger. All seemed well until today. It shifts through all 6 great, but it's revving high and not going much. Had to creep hope. And there's a funky smell. My initial feeling is clutch, but again, there's absolutely zero issues when shifting. Any others experience this?

 

If the tach revs but the speedometer doesn't then you're slipping between the engine and transmission, yes that's a burned clutch.

Smells like toxic burning chemicals, very distinct when you smoke a clutch or brakes. Sometimes it persists for hours with a clutch as the smoke works it's way out of the bellhousing.

If that's the issue then you might consider going to a twin disc, it's a LOT more aggressive compared to a single disc clutch but it's also got a metric F-ton more friction which helps improve it's life in high horsepower applications.

You will loose that smooth clutch pedal feel though, it quickly becomes an on/off switch.