I doubt there's anything wrong with the car making it slower, it's just a stock Cobra with stock gears, and he didn't drive it hard. Slow and un-impressive sounds about right.
Until you take it wide open and run it to the redline on an otherwise stock car, it won't be impressive. It'd feel better with steep gears, but assuming it has 3.27's it's just a turd until you give it room to run.