2002 jetta shakes horribly

I have a 02 jetta gls 1.8t that i have owned for 3 months. I bought it certified thinking this thing is in excellent condition. Well i have a problem. before this thing gets up to about 45 mph. it shakes horribly. i have had the tires rotated and balanced and it didn't touch it. i have had someone say it could be the transaxle. don't know. vw dealer wants $89 to just look at it. any ideas. also the turbo feels very sluggish will not fly like 3 months ago
thanks:shakehead

certified = its warranty.

They are taking advantage of you making you pay. Certified means its practically everything is covered under warranty like the normal vw warranty. (accept stuff like wheel ballancing and brake pads and tune up stuff)