When driving my A3 1.8 Sport (1998). I often experience a power loss. Say I am crusing at 90MPH the power will drop of & speed will keep dropping until I change down accelerate & change up speed returns to 90 MPH.
Also there seems to be an acceleration lag when changing from 2nd to 3rd.
I have had the throttle body replaced but this didn,t cure the problem. the car has been back to the garage half a dozen times & cost me 600 pounds but still no cure.
Any ideas

How about loss of boost pressure or vaccum?

Suggest you also check out the TT forums to see if they can offer anything, since it's the same basic system.

The engine is normally aspirated no turbo