Mine has a 085; used the install instruction for the 088, and they appear t be the same except for the airbox.
States in the instructions that you have to trim that triangular chunk off of the trans for downpipe clearance. The one your down pipe is hitting in your first pic.
At first, I left about 1/2" of it left on the transmission, and the downpipe rubbed on it and squeaked, so I knocked another 1/4" or so off of it, and everything clears now.
A sawzall makes really quick work of it from under the truck. I was able to trim it the 2nd time without even removing the downpipe.