I just did the fpr test recommended in the FAQ, where you guage the outlet flow. It gave me about 1/3 of a gallon in a minute, which is a little low compared to the suggestions there, but more importantly, when I removed the vacuum from the fpr, the flow only decreased slightly (and the engine revs went up slightly, as might be predicted with increased fuel pressure).

I'm assuming that in order to have residual pressure in the rails for startups, the flow should have stopped when I removed the vacuum. (If indeed this is true, maybe that should be part 2 of the test)! If removing vacuum doesn't shut off the flow, I suppose there's a good chance that with vacuum, the flow is too high also, and the pressure in the rail therefore is not as high as it should be.

At any rate, if indeed I need a new fpr and go ahead and replace it, does anything need readjusting afterwards? My idle mixture adjustment worked fine last summer; I was able to achieve closed-loop operation with my new O2 sensor by adjusting the AMM turnscrew. If a new fpr increases fuel pressure I assume it would result in more fuel being injected. When the O2 sensor senses this, how then does the ECU compensate? I will check the idle mixture adjustment, but should this be required?