revs dropping when dipping the clutch

[uplink1001]

HI..
I asked earlier if anyone had any idea's as to what the problem may be with my car (Passat 1.8 20v SE petrol).

When i dip the clutch when slowing dow to brake in traffic the revs drop to around half normal idle, at night when this happens the lights dim just for a second or two and then it jumps back to normal idle.

I have checked the haynes manual but the only thing i can find in the fault guide is that maybe the air filter is clogged, (this i changed but no fix)!!

It has not cut out completley (YET), but it is getting a bit of a pain when driving.
Has anyone got any idea's a to what the problem may be, any help would be great..:confused:

Thanks (great forum)

[Eddie]

When u r at idle at the traffic light is the tickover rather erratic ie going up and down without u touching the throttle.Ed

[uplink1001]

sorry taken so long to reply.
when at the lights the car idle's fine no probs, its only when i dip the clutch to stop and slow down.