Could a GPIO be configured to monitor crankcase pressure? I wanted to plumb a MAP sensor into the crankcase to monitor blowby and or detonation.

You could do something similar to what 1fastacvw is doing with fuel pressure. Gets 0-5v transducer (there are partnumbers for one that works here), and run a GPI as Voltage input. The solution isn't perfect but it should get you the info you need. If you need to measure vaccuum as well, you'll need to use a map sensor (or some other absolute pressure sensor) instead of the transducer listed in the other thread. Keep in mind that you'll need to find either an oil-safe sensor or mount one of our MAP sensors so it can drain because you will get oil in it. Wiring for a MAP sensor or one of those transducers is pretty much the same. I'd need to look up the pinout on the transducer if you end up needing it.

picked up fuel pressure sensor today and am wiring it, also picked up map sensor to see what kind of pressures are in the case. im glad you mentioned something about hanging it upside down, ill have to re-mount the map sensor.