Whats up guys!! Im new to this forum and wanted to share some info. I have a 2001 GMC Sierra 2wd with a 5.3L. Pretty much all the bolt ons you could do with a couple bucks. After a while of adding performance bolt ons, I noticed on the highway at cruise on a flat road or downhill that my overdrive would kick down to 3rd gear then back to overdrive over and over non stop. I noticed it more when It was hot outside let's say around 90 degrees plus. It drove me crazy cuz it just wouldnt stay in overdrive. If I give it more gas it will stay and pull in overdrive. So I cleaned my MAF sensor as I have an oiled cone filter on the intake. Still a problem. Took the throttle body off and cleaned it and also ported and polished it. Replaced the TPS and IAC sensors as they were bad. Still a problem. I reflashed my computer and retuned and no change. Added a heavy duty trans cooler and still a problem. Then I looked at my MAP sensor and did some research. I took it off and noticed it had some dirty oil on the tip. I replaced it and that fixed it. I didnt have bad idle problems or hesitation. But it seemed like the performance of the truck was a come and go. One day it would run awesome, then the next it seemed as if it went back to stock settings. After replacing I noticed my coolant temp has gone down, thinking the computer was running lean and creating hotter combustion temps. I have been doin so much research on this cuz many transmission shops have told me my 3-4 clutch pack is gone. But it wasn't slipping. I also looked into replacing shift solenoids but, I knew it was a problem with the air intake. Having an ohm meter can cut down troubleshooting time into half.