MK1 Cab - poor idling

[VWnut]

Hi chaps,
My mk1 cab, 1.8 gti has been suffering from a poor idling problem lately. It seems to be coming from a small black box to the left of the engine which sounds like a relay. This has, what i think, a vacuum hose going into it. I replaced all my vacuum hoses recently and noticed that evertime this "relay" clicked the cars revs would drop to 200rpm then pick up to 1200rpm.
Does anybody have any idea what is going on???
Cheers
Tom

[essex_lad]

Don't know off the top of my head but try this link below.

www.auto-solve.com/mech_inj.htm