i had a 01 rcsb 5.3 with a cam,lt headers,no cats,3 inch exhaust,diablo programmer..i sold it a year ago but anyways after i put the cam in it,it threw po300 code but it ran good..i done some research and the reason it threw the po300 code was because the ckp sensor detects a varation at a idle caused by the cam making computer think it had a misfire..but like i said mine ran good..i would try a tune