I would test the fuel pump. Mine went bad, and I chased ghosts for several weeks (all the ones you've already checked) before I tested the pump and discovered that's all it was. You can wire up a switch to the DME plug under the driver's seat that will let you power the pump while the car is off. If you can't hear it running, there's your problem. I know you said you have pressure, but I would think the system can hold some pressure regardless of whether the pump is working. Here's how to make and hook up a test switch:
http://forums.pelicanparts.com/porsche-911-technical-forum/916075-broken-down-near-pt-reyes-ca-2.html#post9139291