MK2 8v digi(pissmeoff) - HELP - revs drop regularly when held constant throttle

[Jezza8v]

Hi there everyone

Im hoping someone can point me in the right direction with a new problem

when I hold the throttle steady at any revs the revs drop regularly but always back up to relative to throttle

ie hold @ 2000 smooth - drop - smooth up to 2000 - drop
hold @ 3000 smooth - drop - smooth up to 3000 - drop etc etc

grrr

Greetings from the UK (near Oxford), pleased to have found this site as this topic has the only reference to our problem, the car is an 89 Mk2 8v digi. We have this exact same issue which developed about 2 weeks after running the car following a rebuild. Repaced MAF sensor and checked throttle switches but no fix, the car is now undriveable due to this problem so getting desparate. I'm curious as to whether you ever found the source of your problem? Thanks in advance, Jeremy.