like everyone else said check plugs and wires get tuned and then ditch the flowbasterd i hated mine after i put the LTs on I also ran for a few weeks untuned after instaling headers with no problems except check engine lite for the o2s that were not deleted yet

 

Sounds like unburnt fuel in the exhaust from a non firing cylinder.. As long as the primary bank o2's are plugged in, and you only changed to headers and exhaust that motor should run just fine.
Check the plugs and porcelin as said before, it only takes a hairline crack in the porcelin to ground out the spark. If you'd like you can run the engine and pull each sparkplug wire off one at a time and then put back, by doing this you will see which if any cylinder doesn't contribute by no change in idle speed or roughness. But, beware you can get a couple shocks if you don't insulate yourself. This way you can isolate if you have a firing issue, whether it be plug, wire, coil etc.

 

Just tune it.
When I put mine on and borla dumped, it would crackle in the headers during acceleration and pop real loud during shifts (like it was gonna blow up). Got it tuned and it cleared up and ran GREAT. Your just running a bit rich is all.
BTW. I drove it like that for a week before getting it tuned.

 

Changed plugs, and it helped dramatically.

Still idles a bit rough (kind of like a small cam) and does the occasional pop-pop-pop.

Gonna throw cats and rear O2's on it first, to get them out of my room and because I hate O/R exhaust, and then tune it.

and i have DynoMax Mufflers on the way. (not bullets)

 

figured it out.
I had a buddy come over and hook a scanner, then a laptop up to it. We were just going to tune it, til we looked at everything.
The stripped plug that was in the #3 cylinder (thanks prev. owner) stripped the threads pretty good, and even with the new plug snug, seems to be leaking compression, and causing a misfire in the cylinder.

Going to try and re-thread it tomorrow, and if that doesnt save it, buy a new head.

Things like this bug the **** out of me after just getting the truck.

 

Re-Threaded it, problem solved.

 

Good to hear its back up and running! How are you liking the LT's?

 

I like the fact I can tell a difference already, but the flowmaster that came with the truck is going in the garbage ASAP.

I have 2 dynomax mufflers on the way.

ALso, any other suggestions for mufflers?
NO:
FLowmaster
Spintech
Glasspacks
Loudmouths
etc like these

Ive kinda been looking at Borla, or JBA (had my eyes on JBA since day one, and cant find a reasonably priced pair), DynoMax, Hooker Aerochambers, and Moroso Spiral Flo's

Any opinions on these last ones?

Setup is going to be LT's, Catted H pipe, and true duals.

 

Magnaflow, Corsa, Borla.

I have a Borla Xr1 and it sounds good but I get the feeling it sounds like a v6 outside the truck under heavy throttle.