I have a check engine light on. I have not got a chance to check it. I was told its a O2 sensor, After i get that fixed i plan on putting a KN on my truck, that will not cause the check engine to throw a code will it?

KN is pretty exp, 500 i think or so. Could I expect my gas milage to go up, if so how much.

 

If you have a pre-catalyst O2 sensor malfunction, fixing that will do wonders for gas mileage. So will keeping the air filter clean in the stock setup and anything that helps maintain the engine factory clean, including the throttle body. I've no idea how K&N claims better gas mileage.

 

K&Ns seem to be hit or miss as far as mileage/power gains, personally I'd never pay that much for a plastic tube that usually sucks warmer air than the stock setup I do however use the filters themselves

Just make sure you don't over-oil it and periodically clean your MAF sensor if your vehicle has 1

 

If i were you i wouldnt spend 500 for a new intake just get a K&N filter and drop it in your stock box. and i have been told to get the airaid tube and hook it to your stock air box with these trucks most of the time your stock set up is will work better then a after market CAI. the airaid tube allows faster and a bit more airflow all in all it would be maybe 250-300 dollars and thats probably still high. Just something to look into before you spend 500 on a whole new K&N.

 

autoanything.com has K&N system for around 250 not to bad

 

your stock air box it a true cold air intake the restrictions comes in with the tube it has baffles and silencers to keep the noise down but hurts flow the cheapest and easiest thing to do is buy an intake tube(cheap intake off of ebay) and a high flow filter 87$ total thats what i did on my tuck even if you have bolts ons unless your making 150+hp over stock or running at around 7-9k rpm you will not out flow that stock box i can give a right up on this if you would like the only advantages you will see(with any intake) is throttle response more noise better flow and maybe .2 mpg increase maybe 1 depending on driving style you will not see more than around 5hp no matter what you go with the max is 15 but doubtful
just my opinion buying an intake kit for more than 200$ is a huge waste
(now i wont even spend over 100$ sense ive been doing it this way)