I am looking at doing the tuning guide on my pump tomorrow, but I have an extra part attached to the pump and it looks like a solenoid with 3 wires coming out of it. Situated to the right of the Smoke screw and it would need removing before I can take off the cover and get to the diaphram etc?

Can take a pic in the morning, but its a manual 300 tdi and now I'm wondering if I have some odd late 300tdi (1998) with EDC?

It is the TPS - throttle position sensor - it's for the EGR - best way to deal with it is to unbolt it, disconnect it and throw it away - oh and disconnect the EGR if you haven't already done so, remove it if you can be bothered.