I have read many posts about how guys are getting CES lights or codes stored after adding intakes or headers & such. I live at a high altitude & have the air intake & headers done. I havent had any trouble so far, in fact, my car seems very receptive to the Halltech and my LG Streets.

Is it possible that guys closer to sea level are already near the maximum parameters of the computer and when adding mods it throws everything outside those parameters, thus causing engine codes?

On the flip side, for guys like me, at high altitude.....maybe the add-ons are allowing the computer to operate in its programed parameters simply because they were only using a small part of the extremes????

Ya, I know....too long to read & I got too much time to think.

 

I'm at 5,200 ft altitude as well. It might have to do with the oem tune from the factory of C5 vs. Z06.
I added a complete BLACKWING filter, smooth bellows and "ice box cover" CAI intake (w/ cut shroud) to my '04 Z16 after I bought the car. I got the annoying lean bank codes intermittently and realized I'd have to drive 300 miles round trip (@ $500) to get a dyno tune to fully use the system and eliminate the codes. Others here say they've never had any codes with their C5 and similar intake systems.
I finally removed the BLACKWING, improved on the oem Z06 intake and have seen no more codes.

 

Thats whats funny, I am pretty much like you at 5200'.....but no codes & much improved engine characteristics after the Halltech & headers. I would have to go to Denver to get a tune, in order to maximize hp output, but it really seems like the engine is operating at full potential as it is.