2002 Volkswagen Jetta transmission problems

Purchased used 2002 VW jetta 1.8 turbo (5 speed) with 34,000 miles still under warranty. Taken to dealership for blown fuses (cigarette lighter), trunk latch, center console, and transmission repairs. Fuse problem was ongoing. Within a few months, a local mechanic installed a small boost gauge on the dash, which was wired into a 10 amp fuse. Within five days, the car was being backed out of the driveway when smoke began pouring from all the dash vents.

Vehicle lost power at highway speed. Further application of the throttle caused the transmission to second from fourth, causing the vehicle to rapidly decelerate from 70 to 40 MPH, at which point the engine resumed normal operation. This happened several times in the span of an hour, and is entirely intermittent. Three VW dealers are at a complete loss for an explanation. The ECU does not return a fault code. This problem occurs completely at random, regardless of fuel level, incline, or throttle position.