I recently purchased an 87 k20 350 tbi. thing was a DOG driving it home I knew it needed more ass for my liking. so on went some longtube headers and away with the ****ty manifolds. next a friend of mine talked me into putting in a bigger cam. cam specs are comp cam cs x4 250x-11 dur @ .050 206 int 214 exh. valve lift .432 int .453 exh. g ot it all timed and valve lash adjust started it up and all was running smooth. nice gain in power. had no tags and with a snowy winter it sat for a while started it up and blowing flames like crazy only from the right side of the exhaust. figured I never done plugs cap and rotor or nothing so I got a set of ac delco plugs gapped to .45 and new accel cap and rotor. wires are new ac delco already on the truck. still back firing from right side only. at this point im lost. set timing about 8 degrees advanced. still no change. compression test got about 120 on the right bank and about 140 on the left. only thing I haven't done is get a chip made for the tbi computer. nor will I. plan on changing to carb once I get some morecash rolling in. any ideas helpful at this point. gotta put cats on to pass inspection but with the backfiring already blowing apart one muffler I don't wanna put the cats on yet.