Silverado high rpm up to 3K rpms after starting have to cut it off several times after cranking to get it back to normal and it started doing it after it sits for awhile, but now it revs up high alot now, I have replaced MAP, MAF, purge valve, throttle body,reset and relearned Throttle body with my topdon scanner, replaced sparkplugs, coil packs and fuel injectors as well!