I have recently installed a K N cold air intake on my 2012 gmc 1500 with a 6.2L and the gas mileage went down and the truck seems to be ...

I have recently installed a K & N cold air intake on my 2012 gmc 1500 with a 6.2L and the gas mileage went down and the truck seems to be hestating when I get on the gas! I did disconnect the battery and I had it put on a machine and no codes are coming up. I am a little frustrated with it right now! Does anyone have any ideas on what could be going on with the truck??? Is my mass air sensor no good??

Try putting the stock intake back on, and see if that fixes things. How many miles on the truck?

The truck only has about 3,000 miles on it! When the stock intake was on the truck I was getting better gas mileage and better throttle response! But this weekend I will put the stock one back on and see what happens. I spoke to K&N and their tech said that the truck might not except the cold air intake do to emissions stuff.

Kinda sounds like K&N doesn't know what they're talking about... I've never heard of this happening before. You still have the stock intake, right?

Yup I still have it (never get rid of them)

Sorry your having problems bud, have the same CAI on my 6.2 with 3400 miles and it runs like a raped ape even with the stock tune and better with a tune.

Make sure all the clamps are tight, you might have a slight leak. I just checked mine after a few thousand miles and they needed snugged up a bit.

Not sure how K&N connections are set up, but I had an issue with my Air Raid when I put it on. The fernco overlap (rubber connection) are somewhat small and if you don't get them really tight, they can pop loose when you hit big bumps. That happened to mine and I had similar symptoms. When I checked it it wasn't clearly noticeable, b/c it was pushed against the TB. when I pulled it, it was loose.

I put the stock intake back on the truck this weekend and it ran normal! So I took it off and re-installed the K&N intake to see if it would run different. It is still off a little! I did take off the cover to the box and it seems to be a little more responsive when on the throttle! I also heard of people doing a crank re-learn on their trucks, this might be just what my truck needs to fully read the intake! Other than that I have no clue what else to do!?

Not sure what a crank re-learn is, but I do know that when you modify the engine like that, you should disconnect the battery for 30 minutes to allow the ECM to reset. I know you did that the first time you installed it, but how about this time?