About every 70 miles my 1990 Mk2 8v GTi loses its a lot of its power and accelerates very slowly. This can happen at any speed, gear, temperature. The only way I can find of resolving the issue is to restart the engine. Even restarting the engine while moving will solve the issue. Each time the fault happens it is exactly the same power level that the car has. This leads me to believe that it may be the ECU going into some kind of safety mode. Could this happen? Any ideas?