I bought a resistor to fit in my passat (99) that does some weird stuff to the Air Intake Temp sensor and sorts the fuel and gives it a bit more oomph. Basically it fools the injector system into thinking it's cold and bangs a bit more fuel in for a biggr bang. Seems to work. I have a Mk1 with a 1990 16v engine - I have no idea where I would stuff the resistor, anyone tried it?