You said the sparkplugs were wet. Are all the sparkplugs equally wet? If the fuel fouling is not equally present on all 4 plugs then it would be appropriate to check the main injectors for leakage. The check is similar to the check for the cold start valve. While still connected to the supply rail, carefully remove all 4 injectors and then pressurize the fuel system by allowing the fuel pump to go through its prime cycle. A leaky injector will show up as dribbling at the injector tip. If you do this test have new replacement seal for the injector tips on hand because the old ones will likely not reseal when you re install the injectors if they are more than 4 - 5 years old.

Both the intake air temperature sensor (in the front cowl) and the coolant temperature sensor can affect fuel mixture. For the air temperature sensor the service manual values are about 340 ohms at 20 C and 240 ohms at 30C. For the coolant temperature sensor the values are about 2100 ohms at 20 C and 1400 ohms at 30C. Check the sensors using an ohmeter. There is quite a bit of variation between sensors. It is easy to have a 200 ohm deviation on the coolant sensor and a 20 ohm deviation on the air temperature sensor so don't throw out a sensor just because it is not exactly at the service manual values.

Check the condition of the wiring to both sensors and the condition of the plugs. The wiring to the coolant sensor is particularly prone to heat damage. If you have a bad electrical connection to either sensor the increased resistance causes the controller to read a low temperature. If there is a bad connection to the coolant sensor the controller will perpetually apply warm up enrichment (the equivalent of running with the choke closed). If there is a bad connection to the air temperature sensor the controller thinks the air density is higher than it actually is and adds more fuel to mix with the higher O2 concentration. Air temperature sensor problems use create smaller errors in fuel mix. A coolant temperature sensor problem has the potential to create a big mixture error.

You said that the engine has a vacuum measurement of 20 in at idle. Is that 20 in of mercury and is that a gauge measurement or an absolute pressure measurement? I am guessing that it is gauge measurement because you call it vacuum. You tagged the title 1800 1970 so I am assuming this is a 1970 B20E. If you still have an original D camshaft in it that is way too much vacuum for a B 20E with a D cam. With an idle speed of around 875 RPM the B20E runs with a manifold pressure of about 60 kPa absolute which is -35 kpa gauge which is about 10 - 11 in Hg gauge (all at my elevation where atmospheric pressure is around 95 kPa). If your manifold vacuum truly is 20 in Hg then your air filter is clogged or your camshaft is worn out or the valve lash is really large. The last two items effectively reduce the camshaft duration and overlap which can increase the manifold vacuum.