When I installed my dp on my car I got alot more noise as well, I'm assuming that it's from not being catted. As for the vibration and what not, I would say to go through and see if you can't reposition it somehow with all of the nuts/bolts loose and then retighten everything. When I did my exhaust, this is what I had to do.
Unforunately, the only real fix is going to be getting a catback as well. Then you shouldn't have any more fitment problems.
My car is well, it's like 10 lbs of shit in a 5 lb bag...
<------ Click to see what I'm workin' with. ;)