Sorry to keep bringing this problem up again for the third time, but I'm desperate -- the car just flunked again today, and now I've only got two weeks before the car ('84 B23F, LH2.0, automatic, 240K miles) is condemned: running out of time to fix it after failing state inspection (so far retested 4 times). The car's HC emissions are way too high (especially in NJ's new "fast idle" phase of its new test protocol) about 4-5X too high based on the several times I've had retested (although this last time at "slow idle it's a little lower but still in violation), and yet the other gases (CO, CO2) are low.
And this is relatively sudden, as only two years (and only 8.000 miles) ago it passed easily (as it always used to), so there has been some sudden catastrophic change, not something gradual over its life.

QUESTION:Is it possible (or likely, based on the problems described) that I've got a bad ECU (it's original, showing p/n 0 280 000 510)? That, or my distributor (also original, p/n 237 508 003), which shows by timing light a slight variation, about 3 degrees (between 6 and 9 deg) at idle although is steady at higher rpm (maxing out at about 30 deg), are the only two things I haven't replaced yet?

Or is there anything else that can be causing this very high HC that I haven't addressed (see below)?

The idle is admittedly very *rough* compared to my '93s, although the engine pulls very strongly on the highway without any bad spots along the rpm band; but coming off idle for sudden accerations (e.g., from a stoplight), there's sometimes a subtle cough (backfire?).
It's been run on synthetic oil (and doesn't use any between changes), and only on *premium* octane Exxon and AMOCO gas, since I bought it in '86 with only 30K miles on it; and I drive hard, keeping the rpms up by using the shift a lot, so I wouldn't think of carbonization.

To recount my work, and the parts I've thrown at it (without regret) so far:
All vacuum lines (new, silicone, and including those to the fuel-carbon cannister) and PCV hoses (and flame trap) are new and clear, and larger ones are clamped to prevent leaks; also the AMM-to-throttle body ribbed hose is new (and clamped) to preclude any hidden cracks.
The throttle body has been thoroughly cleaned (with new gasket), and the throttle position switch is perfectly positioned.
New fuel pressure regulator (2.5 bar).
I've listened to the fuel injectors (with an electronic "stethoscope") and they all have consistent clicks); and I've checked their individual resistances (all are about 16.6 ohms, compared to 16 ohm specs) as well as their combined (at the ECU plug) of 4.8 (instead of 4.0, but below the 5.6 indicative, per the green manual, of a bad injector).
New O2 Sensor, and new (factory rebuilt) AMM; likewise, new (factory rebuilt) IAC (and new hoses and clamps for them). And I set the base idle to specs (although it isn't a smooth idle whether at base or regular).
Of course, it has new plugs and distributor cap and rotor (and the wires have been checked and have equal resistance).
The temperature sensor checks out perfectly over a range of temperatures (measured at the ECU plug); and I've checked all the other wiring connections (at the ECU plug) spelled out in Bentley's table d (pp 241-12&13) for the LH2.0 system.

The new AMM was factory set to 380 ohms, and I adjusted it further to get swings on the O2 sensor (approx. on a DVM -- it's hard to see swings with the digital display), but it swings up and down mainly at faster rpms (~2,000 and above) -- I don't see such swings at idle, even though the O2 sensor must be really heated up (just moments after a suburban 5 mile drive in 2nd and 3rd gear which happened to be between 2 and 3,000 rpm).

In addition to following Bentley's chapter 241, I've been step by step through Volvo's green manual for the "LH-II" system (model years 1983-4), and haven't found any significant problems (except hard-to-see O2 sensor voltage swings, preceding paragraph). There's little by way of actually testing the ECU; it's almost always be elimination. Likewise, distributor testing is largely on a test bench, not in the car.

I really don't want to have to junk the car -- I'm desperate.

Thanks all (and especially for your tolerance of my repeated inquiries).