I haven't been back yet, but I did pull out my old fuel pressure test kit for the next time I go back to it. It has a spring & diaphram regulator built into the TB assembly and a return line back to tank, like many modern MPI injected auto engines, so if there is an over pressure problem its probably a restriction in the return line. Unlike automotive fuel injection, it doesn't have a vaccum line to the atmosphere side of the FPR, so its not designed to alter the pressure with engine load. It does have a MAP sensor to gauge engine load, and they are cheap so I've already ordered a new one, and I plan to replace the vac line to it when I replace it. I've also ordered an ETC since they are also cheap, and a known failure point on GM engines (and a faulty ETC will often make the ECM think the engine is ice cold and therefore over fuel the engine). The injectors have no visible fuel flow when unplugged, so I think the Orings are ok, and since they are above the throttle plate they wouldn't be a source of vaccum leak. Speaking of vaccum leaks, I should probably replace the pcv and its rubber grommet in the valve cover too. There isin't much else on this to to leak vaccum other than the intake manifold gaskets, and I don't even wan't to think about that.