I have never kept a car more than 30 days without performing some performance mod. On my Mustang, a CAI, Underdrive Pulleys, Iridium Plugs, and C&L Intake Plenum were all I needed for low 13's. The GTO makes mid to low 13's stock, so without tearing into the engine interals, what can I do to get some more ponies? I already have a K&N CAI and a B&M Shifter. Are there any aftermarket underdrive pulleys? Also - is the Predator Tuner worth the cash? Thanks for the input.