I just installed and tested a Cortex tuner on Mike Haddad's dyno. Haddad Motorsports is in downtown LA. Steve registered and downloaded the program for my 2009 GT on the Cortex Tuner, (Premium Sport Red) Mike ran two base line runs. The #'s were a constant 331.3 HP with 341.0 TQ in stock form. The tune was Cortex custom with changes to 91 octane, Shift pressure Superchips tune, Speed limiter Superchips tune. The first pull was 337.3 HP and 344.6 TQ. The overall torque curve stayed high even after the 4700rpm peak. Well this is not jaw dropping and you might laugh or think this is a bad deal, but.......... DRIVING IS AMAZING. The package on the road makes this car feel and run fantastic. The 1-2 shift just about pitches the car sideways. I even got a sweet little chirp on the 2-3 shift. Downshifting in sport mode will spin the tires at 40 mph.
I spent a bit of cash for the tuner until I can take time to install a MagnaCharger and it was good money spent. If you want real big numbers and expect to rip it up on the track, you might need to look at some other source for horsepower. But if you just want to improve your driving experience, call Haddad and get your Cortex.