Vibration and slower with poss. misfire

Maybe someone can help:

my 86 944 turbo had a timing belt/w pump /and supposedly the Bal.ShBelt. done ; the day I picked it up I noticed it was overly loud and vibrating when I reached 2-3000 rpm. The boost is fine, but the amount of power and seemingly strain is odd as it hits as low as 2-3000 rpm. At 3000 rpm the engine has a loud annowing vibration(whether it's in gear or not the vibration /rubbing sound is apparent). A couple people had said the timing may be off a tooth or balance shaft belt is the problem. Another mentioned that it appears as a random misfire and may be due to the Fuel press. Regulator. The shop that did the t. Belt had done my past 944's over the years and I'm pretty sure they know these cars well, but they feel its ok etc. I know its not and want someone with a brain in the Phila. PA area that I can trust take a look.
Also, the wires , cap, rotor were also replaced and fine before the episode. The only other thing i can think of is to replace the Ign. coil.

Any advice wil be great,
Thanks
clsm7@comcast.net
CL

If you r balance shaft is out of time you will get a horrible vibration at 2350 rpms. sounds like they may have missed a tooth on the timing belt. I can't tell you how many screwed up belts I see at my shop. People commonly mix up the tensioners or put them on backwards. I would complain to the shop and have them double check the work. It doesn't take long to check the marks and its easier than fixing bent valves when the belt breaks because it was installed wrong. Good luck