Sounds like the problem... all these symptoms could definately be attributed to a quick spin of the wheel while the steering shaft was disconnected! It has happened before but be thankful its much less of a PITA than the duramax and the part is cheaper!
The best thing to do is find someone that will custom bend a 4" DP from 4" mandrel tubing at a muffler shop. I had it done in bakersfield ca at Bobs muffler and that is the only true 4" DP. If you have a bolt-on DP and you measure before installing its a lil shy of a true 4" ID. The problem is...