I'm plagued by my '84 B23F (automatic transmission) not passing emissions:
HC is way too high, about 800, compared to 220 allowed, both at idle and at fast idle (new NJ state tests). BTW, CO is very low, around 0.03 compared to the state's 1.2 maximum allowed.
And seemingly something abruptly changed since my last inspection 2 years ago (different testing protocol, though): in '04, the HC was 33; in '06 it was 21; in '08 it was 36.
[BTW, the engine has 240K miles, seems in great shape mechanically -- amazingly no oil consumption between changes at 5K miles (synthetic oil since new), perfectly equal drop in rpm when I pull any plug wire (although I've never done compression tests), and better acceleration than on my two '93 240s].

I've done the following so far:
ignition tuneup (new plugs, rotor, cap, and checked the wires for resistance) and air filter (hot air preheat passage blocked);
factory-rebuilt IAC (it wasn't like I blamed it for the high HC, but the idle was terrible, and now the idle is set to specs and very smooth, for a red block);
new O2 sensor;
new fuel pressure (2.5 bar) regulator;
cleaned the throttle body (and new gasket);
all new vacuum hoses (and "ribbed" fresh air hose between AMM and throttle body);
all new hoses and such for the flame trap system;
good clamps on all hose connections;
checked for air leaks with propane around the fuel injectors and intake manifold;
and I set the AMM's pot (CO adjustment) for 300 ohms (I don't have a gas meter to actually set it based on gas levels).

QUESTION #1: The only thing I didn't accomplish is trying to change the coolant temperature sensor (rearward one, under runner #3) -- I just couldn't get to it, even with the throttle body off.
Is there a point in the harness elsewhere where I can check its resistance to see it it's the problem?

QUESTION #2: And now I'm thinking: what about my cat? I've always thought of it only for NOx and CO, but does it help reduce HC also? My CO is very low, 0.03 compared to the 1.20 standard, which makes me think that it's still working, but is this a valid assumption?
If it does control HC, how can I check that it's working?
Can I check it easily, with (for example) a IR thermometer to determine its operating temperature?


Thanks all, in advance.