Hi,my 03 envoy was driving just fine till about 7-8 days ago my check engine light came on ,then tonight i was driving a couple miles from home i had gone to my son house ,which is 9 miles from me ,then i retruned back home i was 2 miles from home an Reduced Engine Power ,light came on an i couldnt go over about 30 mph but i shift to 1 gear up the hills an got home ,can someone tell me what it might be ,TPS, Throttle Body ,Maf sensor ?? thank You ,this envoy has 231,000 miles on it i just replaced the transfer case, after the organial one clutch pak came apart an wore a hole in the side of case ,i put another used tr case on an everything was working fine, now this ,i do need to give it a tuneup ,any ideas,thanks