HELP!! wHATS THIS PART CALLED AND WHAT DOES IT DO?

On the side of my metering head there is a round valve type solanoid that is plummed in to it, on one end with a thickish plastic tube bolted on with the same kind of bolt as the injector pipe and on the other end via a metal fuel line and then there is a plug connector on it with 2 wires all held on to the metering head with a metal bracket and a 10mm nut.I have a 93 clipper gti 8 valve and have been told this is the problem with my car is running rough whilst warming up. And has anyone got one.

A picture may help  

will try and get one on later

Does this help? please  can anyone tell me what this does and if there is anyone got one.