Have no clue what's really wrong.

[MommaBurt]

I would check the other sensor values off the bat. Sensors like barometric pressure, turbo speed, and exhaust back pressure. Really, you should check all of them. I would also double check that you got the correct IMAP sensor for your truck. It's more of a lack of charge flow code than a lack of boost pressure code. I can PM you more info if you'd like.