[KMPrenger]

Well, now your entering into a new ballgame.

Shorties if installed correctly should not throw a CEL. I'd recommend the DT shorties if you went that route.

Otherwise if you go LT headers you will certainly get a CEL. Doesn't mean you have to tune, but you will probably want to eventually. Which opens us up into the long running discussion of whether or not GM can easily see a tuned V6 ECM. Most of the evidence says there is no flash counter, but who knows?

Again it boils down to the risk you are willing to take on, because if GM did find out you were tuned, say bye bye to that warranty!

Good luck!