I have a 96 305 vortec. i had to take the hood off of it to put on another truck so i could sell it and we had a really big rain strom that night then a couple days later i started the 96 305 and it ildes at 2000 rpm now and while driving it it will shift all the way to 3rd gear before i hit 35mph. it also shifts like im tacking 5000 rpms! ive checked the MAF and it seems to be working and ive changed the throttle position scensor but no change. any help would be greatly apriciated.

 

Check for any vacuum leaks. Maybe you snagged or nicked or pulled a line when changing the hood?