2000 Volvo S40 vibration

Hi,
My name is Justin. I own a 2000 Volvo S40 1.9L turbo, it has about 102,000 miles on it. Sometime last month a strong vibration started to occur. Both CEL and SEL came on. While at lights the vibration is strong (during idle) but when I press on the gas the vibrations decreases. I have hard starts from time to time but not often. My steering wheel shakes from the vibration. I have already had a tune-up about 2,000 miles ago. I went to a shop and talk with a mechanic; he said it sounds like a fuel injector. I was wondering from what I have said could you give me some possibilities, before I go out and spend a bunch of money on things that I should have to replace. And I noticed that my engine mounts (passenger side) bolts (two of three) have sheared off due to the vibrations. If you have any at all suggestions please email me at hopgood30@hotmail. Com