Vibration Problem
What I did was I took off the balancer and had it checked at the local machine shop just to rule it out. Mine was only out a couple of grams which is hardly noticble. Make sure there is no part of the engine thats in contact with any steering component or exhaust hitting any parts of the body. As long as your motor mounts are the rubber insolator type, they should isolate any small engine vibrations and not let them transfer to the car body.
Make sure that there isn't anypart of the exhaust system touching the frame up front. I had one spot that my headers were super close to the steering gear, so I had to do a minor crimp act at that one spot, but like I said, mine ended up being in the clutch. If you had everything disconnected up front and it still did it, the only thing turning at that point is the crankshaft balancer. If that checks out okay, then you need to look to the flexplate/torque converter area. That's the biggest external mass that's turning. If something is loose or come off, then that would show up as a vib. If all that is okay then you'll have to look at possibly internal engine issues.
Good Luck!