Well just got back from dyno tune, apparently the stumble was from the fact that I did not install the black cover over the air filter. (Had a flat stumble at 3000rpm) That thing stops the air turbulence from the radiator fan and wind from the road. Without the guard it screws with the maff airflow sensor. I had no idea they were that sensitive nor did the instruction ever say to put it on. I figured it was for show. Anyway the tune that came with the kit was within 10% of my tuners tune. He said he could get about 20 hp more out of it but didn't want to take my money. So that saved me $300. The car is running safe and I am happy with the performance. Vortech did a good job with this non cooled kit.
2006 Mustang GT, MGW Shifter, Flow Master cat backs, Custom Paint, Vortech Supercharger Standard kit 420 HP, J&M lower control arms' Steeda panhard bar, aeroforce gauge, True forge wheels, SR performance springs