EDIT:

Deleted my post, as I found what you were talking about. That's for the N/A only and again, others have reported it is of no use.

Want more performance? Put in a nice, aftermarket CAI, bigger throttle body and even a smaller supercharger pulley, then get one of the tuners to tune it - and you WILL be impressed.
I understand the CAI is $500-800, the TB is $150 or so, and the pulley is $600-800. The tune Iv'e seen advertised runs $400.

I've driven three SRTs modded like this, and W O W are they a different car. As part of the tune, they also alter the transmissions' personality which adds a lot.