OK did a huges intake swap headers and rockers 1.7 new plugs wires cap rotor now i have a misfire when im cruising at about 1400-1500rpm's and backfire out of tail pipe did not think i had this before what can i ck for also when i start it up sometimes when starting it will bumble like i have a big cam no throttle response will shut off if i give it gas , i turn it off then back on and everything is normal what else do i ck for ????