How do you know when its time to replace the air filter?? May be a dumb obvious question hehe but just curious.

If you hold it up to the sunlight (do not look directly at the sun), you should be able to see light thru the filter. If you can't, it is time to replace.

//2000CAYukon

ok well i havent tried that but it looks pretty filthy and doesnt look like sun will shine through it. Thanks for the tip. Oh and what is the litte clear cylinder thing on the hose conecting to the air filter chamber? Its got a button on top and a green line around a cyclinder inside??

That little clear cylinder on the intake tube is an air flow meter, it is suppose to tell you when the air filter is starting to plug, it will slide up showing a yellow ring under the green ring. I have never trusted them though, I would change the air filter way before the yellow ring is exposed. I change my aif filter every 12,000 miles or once a year, but I spend quite a bit of time in the dust and dirt.