what could i gain from this if anything? could i lose low end, or gain top end

 

Without any supporting mods: mid pipe, headers, ect. you won't see much. The only thing you will notice is a more agressive sound which will probably fool your mind into thinking your going faster but your not. Catbacks really only show their potential over stock when the car is modded.
So what are your mods? or should we keep them your secret?