MAP sensors and adjusting them

[3VILC]

Heres one for the technical guys.
Using an ECU from a 2.0 engine on a 2.2 engine:
If it used an airflow meter, the extra air drawn in by a larger engine should be accounted for and no problems should arise. However because it is using a MAP sensor, which I assume is calibrated inside the ECU to 'guess' the amount of air at a certain vacuum based on the engine size among other calulations, and because most engines produce the same/similar vacuum at idle, it is only going to assume enough air for a 2litre engine is going in and inject enough fuel for this.
I imagine that the extra 200cc's would be enough to create a lean idle condition and the engine would idle like it had a really bad vacuum leak?
Am I on the right track so far? This is the symptom I am getting, yet an actual vacuum leak on a MAP sensor system shouldnt have any effect other than high idle since the sensor will still detect the drop in vacuum.
So, since the MAP sensor essentially behaves like a variable resistor, in theory at least if you used a simple adjustable voltage regulator circuit, you could slightly increase the 5.0v reference voltage into the sensor which would in turn slightly increase the output voltage sent to the ecu, tricking the ECU into thinking the engine is slightly more loaded and injecting slightly more fuel. Adjust until the idle comes right and all should be well.
I have read of this method being used to increase fuel delivery before so it does work at least on some engines.
Is my theory correct, or is my thinking utter rubbish and its just not going to work without an aftermarket ECU (in other words I should give up and bolt the crappy carb back on).

Any useful input or other thoughts or ideas is greatly appreciated.
Cheers,
Clive

[kbushnz]

Is this what you want to do???
http://jeep-xj.info/HowtoMAPsensor.htm

[3VILC]

That is more or less the same thing I was looking at..interesting they say it only uses MAP above 80% throttle, but then it is for jeep.

[bob_or_jim]

Another option could be to fit 10% larger injectors (didnt read that artical so it may have had that in there?)

Or play with the fuel pressure to get the right flow. Would need an O2 meter to tune this though. Fuel pressure regs are probably cheaper than 4 injectors.

Worth a thought anyway.

Cheers