Whats wrong?

when my truck (05 6.0) is cold, the exhaust fumes in the truck cab get really bad. Also, with the tuner on the high level, when i give it the green one smoke wil come through the vents into the cab. what could be the problem? i'm thinkn maybe the up-pipe is leakn...? also, it seemd to get worse aftr the egr cooler wz replaced under warranty...could it be loose or somthn? thancks for the help!

I would think exhaust leak. Set your tune to whatever smokes the most, have someone give it some throttle, and see if you can see anything under the hood.

Probably a cracked passenger side up pipe..very common for them to crack in the flex section.