I agree that it sounds like rich mixture. I don't have that problem with my Regina 745, but have been battling it in my 244. I have those same codes and I do foul my plugs fairly quickly. After it's been running or especially trying to start without running, if I remove a plug it is wet with gas, but if it has been sitting, the plugs are dry, but coated with black soot. I think the soot is the real problem with the plugs firing. Cleaning them helps, but a new set is only about $5.

Then to diagnose the underlying problem. Lack of air is unlikely. Lack of spark is possible if wires or coil are weak. Seems like the most likely suspects are too much fuel pressure, caused by a bad fuel pressure regulator (see the FAQ for diagnosing that), leaky injectors, bad cold start injector or a bad (or disconnected) coolant temperature sensor for the ECU. I think the last one is my problem, but that is a difficult to get to. Hopefully today ....

Look at the FAQs for locations and diagnosis of those items, but one trick I thought of on my own for eliminating the cold start injector as being stuck open was just to pinch off the fuel line which goes to it with a C clamp. That made no difference for me, but at least now I know that isn't it.

I'm hoping for you that it's the fuel pressure regulator. That is SO easy to change! If you have a non-turbo '90, then I believe that you have Regina EFI, in which case you should know that everyone says (and I have done this) that the FPR for the LH 2.4 system works identically to the one for Regina and costs half as much.
--
Andy '91 745 186K, '89 244 135K, '87 245 lost the rust battle at 225K mi