Well after a bit of traveling away for work, a grand tour of New Zealand's South Island and helping out on another project last week I have finally been able to get back to my own fuel injection project.
I had the pseudo MAP co processor working and responding as hoped. But I was puzzled for a bit about why, when the throttle was completely closed the crankcase pressure went up. On reflection I figured that when there was no suction from the pipe atmospheric air and exhaust fumes flooded back up the exhaust pipe and through all the gaping holes in the cylinder.
Filling the crankcase to near atmospheric pressure with dirty exhaust gave the underside of the piston something to compress resulting in a misleading high pseudo MAP value. The crankcase pseudo pressure quickly dropped, actually the difference between max - min crankcase pressure dropped as soon as the pipe started sucking again and the piston was left chasing air that was rapidly disappearing up the transfer ports.
Some tweaks to the co processors software soon sorted that and now my two strokes pseudo MAP value looks much like you would expect from a four strokes MAP sensor and hopefully will be a good indication of changes in mass air flow for the EFI's CPU to work with.
I expect, with a bit more software tweaking and some time tuning the fueling map with Tuning Studio I might soon have a fuel injected two stroke bike I can race.