I'm interested in opinions/viewpoints on this. Here's the deal:

- 1984 380 SL, owned the car for 10 years
- The car is only driven about 3000 miles a year maximum. It's a second car.
- Current emissions test good for 2 years from now.
- Just spent thousands on various repairs done by myself and a mechanic including new rebuilt fuel distributor (mechanic), injectors (mechanic), a new idle control valve, new CORRECT plugs and Bosch wires, new rotor, new distributor cap, electrical fully investigaged (me and mechanic), for cooling a new radiator and fan clutch, new fuel pump, and new fuel filter.
- Car now has a lean idle miss for any CO idle adjustment below 1.8%. The Mercedes shop manual for this car suggests a CO value in the range of 0.5 to 1.5%. For 10 other years of its life with me the car always sailed through emissions HOWEVER apparently one of the two precats was clogged and the car lacked power-- for 10 years I apparently had no idea how much power this car could really have-- even now if I set the CO value low and live with a lean idle miss, the car has tremendously more power. The rest of the emissions values fall into place and are what you would expect at 1.8% (NOX around 1500, HC around 200, CO around 14%, O varies but usually zero since we are clearly running rich).
- I don't care if the catalytic converter hates this 1.8% value, I'll eat it later if I have to on a new cat.

When set at 1.8%, the car drives perfectly in every respect-- smooth-as-silk idle, incredible power, instant startup (always had a good startup). About 20% reduction in fuel economy as-expected with such a CO setting.

I presented this to several mechanics, here is what they say:

Mechanic #1 who, who has made errors with this car charging me thousands for repair work that resulted in nothing, states it's a manifold vacuum leak (without him doing a full vacuum check on the car by the way). He wants more dollars to do the job after sucking an embarrasing amount already (he's the one who has now spurred me to do as much work as I can myself on the car after my experiences with him). OK, it certainly is possible the car has a vacuum leak-- indeed likely, however it cropped up during the 2 weeks he messed around with the car. His rebuilt fuel distributor and fuel injectors may be the suspect here, I sprayed around with carb cleaner in those areas though and couldn't find a leak.

Mechanic #2 says "leave the car alone. If we can get these 20 year old cars to be under 2% CO we're OK with it. "When emissions time comes, we'll deal with that however we need to deal with it (translation: adjust as-needed even if it rides like crap to get it through).

Mechanic #3 who runs an emissions repair facility also agrees with mechanic #2-- he states the emission values for the car really aren't that bad, leave it alone.

I've been ALL OVER the car myself looking for vacuum leaks around injectors, the fuel distributor, cracked hoses, etc. The car is very clean inside, you don't find much in the way of old cracked hoses, etc. I've sprayed carb cleaner where I could safely, etc. I'm the one who found this 1.8% sweet spot for the car by driving and adjusting to just a the smallest increment my hand can make on that screw. I know how sensitve that idle adjustment CO screw is so I turn it back to lean then turn it very slightly, put the car in park and rev, drive if needed, turn more as-needed, until I get to the sweet spot.

Everyone around me thinks I should, at this point, leave the car alone-- the idea that me and this car have had enough for now and we're just a bit over what MB has stated as max. Clearly we are working around something here but maybe it's best to quit while we are ahead (or behind depending on your perspective). Other than harm to the cat converter, I can't see much risk in running the car this way for the next two years. It's fun to drive and the engine sounds as though it's exceptionally happy-- never experienced it as smooth and "calm" at rest or at acceleration.