Please help. my 95 jetta lll lights the check engine light & runs a little rough under 3500 RPM. right at 3500 RMP no matter what gear i'm in or if i'm even accelerating the check engine light goes away & there is a tremendous power boost. it almost feels like a turbo boost, but i know it doesnt have a turbo. when the engine is cold the check engine light still comes on under 3500 RPM but there isnt the same hesitation & bogging as there is when the engine warms up. also the tach & speedometer work intermittently. if i start the engine, they will both either work, or not work. this doesnt seem to have any effect on the check engine/hesitation problem. auto shop said snap-on scanner couldnt read the engine code.

You need to take it to VW or find someone with a VAG-COM scanner to check the codes.