KNN has a cold air induction kit. Magnaflow, and other muffler manufacturers make universal fit mufflers. There are Mustang specific suspension and brake upgrades as well.
No offense but with a V6 Mustang
you will probably spend alot of money and not really get big performance gains. Also the Ford pushrod V6 won't sound as good as a German or Japanese 6 cylinder.
Just leave it as a stock daily driver and save up for a GT or another higher output sports car.