Hey Guys

234K on my M103. It runs like a raped ape, idles smoothly. Not a single drivability issue at this point.

Just recently I've done: Spark Plugs, Head Gasket, Dist Cap + Rotor, Air Filter

A few years ago the last time it failed smog: The O2 sensor was replaced with a Mustang Unit, EHA, and Engine ECU.

I'm kind of leaning toward O2 first. It has been about 70K since it was replaced. Or maybe CTS?

Original: Catalytic Converter...could a cat alone cause to fail BOTH HC & CO?

Idle:
HC Read: 392 Limit 120
CO Read: 6.09 Limit 1.0
CO2: 10.8%
O2: 0.2

2600RPM
HC Read: 185 Limit 140
CO Read: 3.14 Limit 1.0
CO2: 12.8%
O2: 0.1