If you had your stock wheels on before and no vibration, it's gotta be wheel/tire related. Make sure you have good hubcentric rings, I got a set off ebay that were supposedly 72.5mm - 74.1mm, but they weren't doin ****. Found a local place that had some in stock and they were visibly thicker. That's more than likely your problem.

As far as wheel offset... you should be right around ET 20. Should say inside the wheel.

If your bearings are shot, you'd probably hear a scraping or grinding.