As I re-read a couple of posts (including my own) which suggested checking fuel pressure regulators, I was reminded of a Fruit-of-the-Loom moment an acquaintance had a couple of years ago. He runs an independent repair shop, and was checking out a full-size Ford truck under the hood. I don't recall what the symptoms were, but with the motor idling he removed the vacuum line to the FP regulator, and gasoline started spraying everywhere! He screamed for SOMEONE to shut the [expletive deleted] engine off, but no one heard him for several anxious moments over the shop noise. Yes, the regulator had failed.

Moral of the story is - be *real* careful removing the vacuum line off the FP reg while the engine is running. If you suspect a failed diaphragm, use your nose and eyes first to check for raw gas on the vacuum side of the reg, with the engine off. Then maybe proceed with a helper available to crank/kill the engine.