Hmm,the plot thickens. I have purchased OBD2 scanner and observed live values. Weird MAP behaviour is only present in neutral. In drive, MAP corresponds to vacuum values the way I expect them to. So I suppose MAP is fine too. Coolant temp reported by OBD2 is correct as well. After car warmed up and I cleared the codes, everything is fine. Short term lambda adaptation is quite large though: at low load it can reach -10% and at high loads +5%.
These cars are incredibly cheaply built. Tiny brakes on 2.5 ton vehicle, plastic (!) brake caliper pistons, leaf springs in the rear, no interior air filter fitted, FPR and fuel filter built in one unit (not even compensated for manifold pressure) that lives on the fuel tank. My working theory right now is that FPR/filter is clogged and providing too high fuel pressure, leading to intermittent rich condition.
I loaded it with injector cleaner, next step is replacing filter
