most that tested the factory '07 GT claimed 14.3's. '05 and newer 3 valve 4.6's had 300 hp factory. He got 13.7's, with really never being able to 60' ft. Probably could have got 13.5's. We'll find out what the Chally runs.Surprised the flowmaster exhaust is considered a power upgrade. Their mufflers are not known for an increase in flow or power. The internal design has been shown to actually hurt flow compared to most aftermarket and even many stock mufflers.
I will say they do sound good on most cars though.