I'm thinking he put the y-pipe back on the turbo and slapped the clamp on it and thought it would be good.
The y-pipe will not properly seat that way, and you will get a heck of an exhaust leak, the turbo wont spool like it should and it will run like a dog.
A quote from the sticky on egr/oil cooler replacement:
When you go to put the turbo back in, have the clamp on the flange of the turbo, butting up against the body of the turbo. Then get the y-pipe set into the turbo perfectly. You might want to run your finger around the connection to make sure it is right. Then while holding the connection together, get the clamp on the connection and tighten it just enough to hold the connection together, but don't tighten it to spec just yet. This is where you have to make sure that the up-pipes on both sides of the truck are lined up with the exhaust manifolds and tighten those connections down finger tight. Then go back up and tighten the clamp on the turbo to spec, then go back and tighten the exhaust manifold connections. This is the best way to get it done right the first time. It really sucks if you have to take this all apart because of a leak. Keep in mind that the clamp on the turbo to y-pipe connection is only there to hold it in place once the connection is properly set and perfect.