Dee Your mechanic may have input the wrong info into his diagnostics machine considering VW have said that they never heard of a distributor speed sensor,i would get a second diagnostic test done else where,with regards to the engine management unit as i have said it can clear the fault codes and your real problem may not show up,your problem could be one of numerous things with regards to losing power.It could be a vacuum hose/brake servo hose which is loose or has a hole in it,,this allows too much air to be drawn into the inlet manifold which weakens the air/fuel mixture causing the car to lack power,and have poor acceleration, thats just one suggestion.If you could post back the year engine size,at what stage during a journey does the car lose power,i will ask a few of my friends that are in the motor trade and i will post back a list of suggestions for you to look at.pm me that you have posted back here as this thread isnt a busy one and i tend to over look the fact that its here :)