I know this has been covered several times, but...I turned a corner yesterday after driving about 25 miles and got on the throttle pretty hard. The truck started bucking and the engine light came on. It has a p0303 code. It stutters real bad if you hit the gas below 2000 rpms, then it runs fine above 2000rpms. When it is cold it hardly does it, but the more I drive the worse it gets. I was wondering whether anybody thinks it is the usual bad plug,wires,coil,oil leak at valve cover or a clogged cat. Where should I start? Tuneup or converter?

99 Sportage 2Dr, 1.5" body lift, 30x9.50 Cooper M/T's, high lift, CB, custom bumpers, Warn manual hubs, Tom Tom GPS, snorkel.
99 Jeep Cherokee 3" lift, 31" mud terrains