I have converted to a MAF & dyno tested it with that and the stock AFM. It makes no difference in power. The flapper door in the stock meter is not restrictive. The biggest pressure drop you are going to see across the meter is like 0.073psi. You lose a lot more than that in the intake ports & intake manifold. Trust me, while there are some benefits to running a MAF, power isn't one of them. The M42's stock air meter is properly sized. M20 motors benefit from larger sensors only because their stock one was too small to start with. They get the same gain from an M30 VAM as they do from a MAF.
The simplest air-fuel control system, and hardest one to tune for a street car, is Alpha-N. It runs from RPM and throttle position alone. It is intended for race cars where you spend 99% of the time at 0% & 100% throttle.
A lot of people have run stand-alone engine management (removed the stock ECU & put a DIY / tunable system). This lets you run almost anything (Alpha-N, VAM, MAF, MAP). However, you will spend a minimum of $2000 on the hardware & dyno time required to get the air/fuel ratio & ignition timing dialed in. You can do most of the AFR stuff yourself, but the ignition timing really does require a dyno.
I understand why you want to delete the sensor. However, it sounds like you are on a budget. If that is the case, forget it. Learn to work with microcontrollers & analog instrumentation & you can do it yourself while keeping the stock ECU. Due to the cost & apparent silliness of the few commercially available MAF conversions out there, I decided that figuring out my own system was a better option. It took a solid 3 years to really get it where I wanted it. Then again, I spent more on electronic development & test equipment than a MAF kit would have cost, so I guess you are damned if you do & damned if you don't :p. That's how just about everything with cars is anyway, though.
Stick with stock & just get a Conforti or MarkD chip. Toss in an M20 flywheel. That's about all you can do for the M42 without spending more than $1000.
