Stillen doesn't offer a turbo kit, a turbocharger has the power come on fairly suddenly and has a tendency to shock the transmission, which exacerbated gear slippage. Stillen's (and I suppose GTM's) supercharger has the power come on very smoothly and is nicer to the transmission.

A VB upgrade is less important in a SC build, but I would do it anyways for peace of mind. Alternatively, a tuner can increase line pressure in the automatic transmissions to combat gear slippage and to clean up the shifts, but it is by no means a permanent solution. It's better to do it right, you know?

 

Yeah let's see if I can get a new VB