348 with too high HC levels at idle (348 guru's needed)

My 348 has been driven very little over last few years but I think I'll be able to correct that mistake from now on. Anyways, I'm now having probs with local emission test even though car feels good and is responsive.
So base information: 1991 348 and no cats (I'm allowed to run it without cats), emission test limit at idle for HC (ppm) levels are 600 but my car was well over 1000, meaning there are lot of unburned fuel. (so its measured at idle car standing still) Even without cats it should be 300 or so based on factory manual, I guess 500 should be still OK. CO levels are within limits, CO% 1.18

Following new parts ignition parts fitted 5 years ago but only 2k miles after that (and car has been sitting in dry and warm garage):
- Magnecor plug leads (I measured those now and all are OK, resistance between 3.5-5kOhms)
- plugs look all OK and about same (kind of grey/brown)
- Bosch coils (but I'll get new ones just to be on safe side)
- throttle position sensors and idle control valves

-I had prob with MAF connector year ago (car was idling badly) but just wobbling connector solved it, and it doesn't have those symptoms now. I would replace MAF's to check if thats the problem if they wouldn't be so stupidly expensive.
-I cleaned crankshaft position sensor plugs but I will replace those when I get them.
- oxygen sensors are are 5 years old but as said, maybe 2k miles. I will get new ones next week and install those.

We measured from both tailpipes and figures were pretty similar, I'm running Tubi exhaust and IIRC there is no real x-pipes built in so I think both banks have this high HC problem.

Major was done less than 2 years ago by well known (and respected) specialist in UK and they should have set timing correctly (hopefully).

So to my real question: any idea what to look or replace? (my guess: as I'll replace coils+plugs+oxygen sensors+crank sensors, that leaves MAF's)

Is is possible that Motronic (2.7) is somehow in open loop mode, so same mode as in startup? What triggers it? (my guess: temp sensor, oxygen sensor at least)
Can it be tested? (maybe disconnecting oxygen sensor while car is idling when fully warm?)

As said, car feels good but it does have some problem at idle. Short term I need to get it to pass emission test (I do have race cats waiting if I can't find problem before emission re-test, that should get me pass). I used to live (and car as well) in UK where emission limits are higher than in Finland so I never really checked emission levels before.
And unfortunately I don't own exhaust gas analyser (have to add that to Santa's wish list) so I can't play with it while changing parts .

 

Thanks! Some I have (hopefully) now ruled out but still plenty to go.
What makes me think (I might be completely wrong) that its not just one cylinder that is playing but whole system: plugs look all the same and measurements were fairly similar from both sides of exhaust.
Forgot to mention that I measured resistance for MAF's and they were bang on what they should be, it still doesn't rule out there wouldn't be problem with MAF's.
And as this is european version, no easy way to pull codes if there are some.

 

Last year it just passed here but it could have been just the MOT man beeing so happy to see Ferrari.
And in UK it was very easy to pass so I never checked emission levels.
I have in papers here that my car came without cats from factory so emission tests are very easy (factory workshop manual says that 348 should be adjusted to 250-300 HC levels before cats, with cats like 50. And we have 600 HC limit here so my car should easily pass without cats, my 1000hc levels indicate unfortunately that something is not right as its hugely off.
So al in all,emission test here is nothing compared to California, at least something is better.

I'll try injector cleaner but I think to do it properly they should be removed and professionally cleaned/adjusted. But that has to wait our long and cold winter. And if there would be problem with just 1 injector, spark plug should have some signs of prob?

I'll have to dig some info about open/closed loop operation of Motronic 2.7