Exhaust smell - GT40

[FMSKI]

So fired up my Gt40 engine (97) last night. Had to reverse the Fuel Cell pump as it was jammed (purge debris) new filter and cleaned that all up. But for the past few years I've felt the mixture was off and the exhaust has a pungent unhealthy smell to it. Might be because I am used to catalytics, but if the mixture is say a bit rich, it will kick off the carcinogens and smog NOX etc.

Is there known sensor drift on the GT40? any things I should try first?

[FMSKI]

Just to update - Pulled the manual and these are the sensors:

MAP Pressure in Hz.
ECT (engine temp)
ACT (air temp)

[FMSKI]

I think I found the issue. The Engine Coolant Temp sensor is reading as if the TEMP = high. Therefore the mixture is leaned out. (LEAN)
I am correct in saying there is excessive NOX and the lean mix has an awful eye-watering smell, from what I have googled.

A rich mixture smells of unburned HC's but not as pungent. So I am getting a new sensor and we'll see what is the difference in K-Ohms.

[FMSKI]

Old ECT sensor was def reading off by a fair bit (engine too hot). My ohmmeter is acting up so hard to get a proper reading.
Installed new and much improved for start, idle smoothness, sound, exhaust smell is gone.

For the record - symptoms of a bad ECT and lean condition are:

Pungent smelly exhaust
Bogged sometimes, when hitting it with a skier in tow
Lumpy idling - occasionally
Had to add a bit of throttle on start during cold temps
Sounded louder too. Thought my muffler was bad

Going to check the ACT as well.