If it were me, I would do a smoke test. The hoses can look good but still leak. How about the other seals? Brake booster? Injector seals? Intake seals? Big rubber boot under the AFM? How about the u shaped hose under there too?You can make a DIY smoke machine for about $20. or take it to a shop that has a smoke machine, if should only be an hour of labor.

No I don't think it is running rich. After the engine is at operating temperature, pull the connector to the O2 sensor. Put the red positive lead of your DMM to the o2 sensor signal wire and ground the negative lead black to ground. Set the meter to dc volts. the signal should cycle from .1 volt to .9 volt. with the middle .45 volts which is lambda. If it doesn't read that, then adjust the 3 mm allen screw until it does. lean is .1 volts or lower rich is .9 volts or higher. No need for a exhaust gas tester. Now the ECU can do its job. This is the way that Steve Brotherton sets the mixture.

Again, I think you have an air leak and you can't detect it until you do a smoke test.

I have two 190e's- a 1992 2.3 and a 1993 2.6. The 1984 190e is a different KE jetronic system, similar but different.