i believe that if you are not running any forced induction applications, intakes, headers, and exhaust wont give any improvements. maybe you will get that 10-15 hp with all 3 bolt ons going at 100+ miles per hour, but for regular everyday driving and street racing, it wont do anything... any inputs are welcome... actually i would really appreciate it if someone can prove me wrong because i do wanna get these bolt ons but its just not worth it for the money. BTW when i say bolt ons, im not talking about generic OBX, Arospeed crap, im talking about full cat back systems, dc sports quality headers and cold air intakes.