[FSU944]

Hi all. Just bought an 87 944 a couple weeks ago and have been reading all I can to get familar w/this car. Today, I failed the smog test. I have no chips installed. Here are the readings:

Idle:
CO2%: 14.10
O2%: 1.20
HC: 123 (Max is 120)
CO%: 1.36 (Max is 1.00)

2500 RPM:
CO2%: 14.80
O2%: 1.20
HC: 15 (Max is 140)
CO%: .08 (Max is 1.00)

I failed the HC and CO% at idle. At speed, everything passed no problem. I noticed the O2% did not change between tests. The shop mentioned the cat may be going, but should I just start w/the O2 sensor?

I did a search, but didn't see any tests that were abnormally high on CO (most were NO2).