well you might want to check fuel filter & pump, than make sure your airfilter is good, than the intake check for cracks or leaks, sparkplugs-proper gap is critical dont over gap,or you'll get random misfire thathe computer wont see- with exhaust, alot of the cats get worn out or plugged over time. i've seen a couple cases where timing wasnt right on cue, and recently ran into a brnt valve. but thats really rare. high miles??(over 75,000 mile) top end rebuild with piston rings (low compression-will lead to doggy dog performance) ;) -by the way, 1st decent question!