Emissions problem

I have an 89 Jetta GLI with the 1.8 L 16v motor. I took it in for emissions today, and it failed the carbon monoxide test at idle. It passed everything else including carbon monoxide at higher rpms. I was wondering where I could start to resolve this issue. In addition, it has been running sort of funny lately. It runs smoothly, but it will often have little power. It doesn't make any weird sounds, it just picks up really slowly. Its like you hit the throttle and nothing is there. I don't know if this could be related to the emissions problem. Also, I had some recent trouble with the oxygen sensor in the cat (possible issue) Please help.

The CO level at idle is adjustable with a small hex screw located under a plug between the air flow metre & fuel distributor. The plug has probably been removed. There may be other problems....

I had that power problem with my 98 jetta and my throttle plate needed cleaned. After I got that done it didn't lose power anymore

Totally different car....