I have a 2006 6.0. After have 3 egr coolers replaced I decided I needed and egr delete. I found an egr spool and put it in the place of the egr valve and left the egr hooked to the wires and zip tied it up out of the way. When I did this the truck went from hitting 30 psi of boost to only hitting 20 psi of boost. So the local mechanic told me I must have pinched or cut an o-ring on the spool. So I took it back out and got new O-rings twice and still could not get above 20psi of boost. So I put the egr valve back in it and it went right back to 30psi. So I put the spool back in it and right back to only 20psi. So I had put the egr valve back in it and had the local mechanic put the block off plates on the egr cooler and it still wont do more than 20psi. Nobody I can find has any clue what could be causing this. I hope someone can help me out.