2000 GMC Jimmy noise when speeding up

Is the noise a whistle? Could be an air leak in the intake plumbing. Or a vacuum leak.

Yes it is like a whistling noise...I also didnt mention that i have an airaid cold air intake...will this be where the problem is coming from? if so how do i fix it or does it have to be professionaly done?

Yep that could be the problem. Since most of them make you think they are adding power by creating a bunch of extra air noise. If yours is like most of the cold air kits they actually pull in hot air from under the hood. Never could figure out how they can call that a cold air intake. The stock unit draws air from behind the grill in a high pressure area, sends it through a system that flows almost 5 times the air that the engine can ever use and quiets it down nicely as well.

Oh and be advised that if that system is using an oiled gauze style filter, those like to leave oil deposits on the MAF and set off the check engine light because of the contamination of the sensor.

Ok that is probably why my check engine light will come on and go off like thirty minutes later. So do you think it will be best if I put a stock unit on my car...the previous owner put the intake system on the car so i would have to buy another one. Or is there some way that i get it to stop doing that?

Have it scanned for the codes. That should tell you what the computer is seeing as a problem.
You should be able to find a used air intake and box easily enough. Try www.car-part.com for a local one. They are VERY easy to remove and install. That should take care of the whistle and may eliminate the CEL as well. That will depend on what is causing it.