Flowmaster 10 series and new pully
 

I have a 04 cobra. It has flowmaster 10 series and I was wondering how much hp that adds? Also thinking of changing the supercharger pulley any advice on what one to use? I was also thinking of putting natto 555 tires on it. Any advice is welcome ty

I think it depends on the engine setup and not solely on the exhaust alone if you want to add gains. Putting a new exhaust will surely make it sound great. you'll get more power gain if you have a combination of pulley, cold air intake, exhaust (stock or aftermarket) and tune.