Idling problem

Hey guys,

Recently changed alternator and timing belts, as well as tensioner (VW Golf Mk1 1.4i).

After changing all of the above, the car has irregular idling. It idles at 1000rpm, then when I rev past 3000rpm, it comes back down to about 500rpm for about a second, then goes up to 1000rpm.

Any ideas.

Sent from my Power 3S using Tapatalk