The goal of the project is to make many people who have their stock ecus fried happy.

The fun part is that there are no turbos or anything else fun in these cars. They are just common shopping bags wanting to go for a few kilometers more. While it would be pure insanity to buy original Mitsubishi spare for 1400 euros or so, it would be very good idea to use something like genboard.

I've been thinking about keeping the original wiring intact and using all the stock parts. So that it would be a direct swap from the stock ecu to genboard. Even the casing and headers would be original. That would give the owner of the vehicle the choise between leaving it as is or making whatever modifications desired.

The question is, is it possible to use the existing air flow sensor with genboard and not to use the MAP?

Possible? Not right now, but possible if you write the firmware to make this happen. :) You could possibly log the air-flow sensor output against MAP and MAT, and work something out from there. OTOH, most systems have a vacuum line somewhere, so you can probably supply a t-piece and some silicon tube to make this work the easy way.

And are there any other issues about making it a direct replacement?

Getting the appropriate connectors could be hard (RichB is looking for a source for Rover V8 (Lucas 14cux) 40-pin ECU connector). Junking OEM ECUs for them initially sounds good, until you find the price of a dead one is huge too - repair is usually cheap, so dead ones are like gold. Custom made cases may be relatively expensive. Don't let all this put you off - it's a good idea!