1999 Chevy Silverado idles high and low

If anyone could help me it would be greatlly appreciated.
whenever the weather is colder my truck will idle high and low and surge. If I unplug the mass air flow sensor it will quit doing this but makes my truck shift harder. Ive changed the mass air flow sensor, fuel pressure regulater and still seems to idle really high and low. An engine scaner says bank 1 and 2 are running lean. Please help! If anyone needs more information I will get it to you!

thanks cody