There seems to be a lot of back and forth about Flowmasters installed on the Shelby GT 500. Rumors about a Flowmaster Rep stating they reduce horsepower etc.

Has anyone done a before and after on the dyno to actually see the difference of factory mufflers, versus any of the three offerings from Flowmaster for 2007-09 Shelby GT 500

If so, please let us know on this forum.

NOTE: I have submitted a trouble ticket to Flowmaster and willl post their response.

Thanks

 

I have the SS verison of the Flowmaster A/Ts. While my car has never been dyno'ed before or after the installation, I can tell you with certainty that I did not lose any HP.