OP - Before you drop your fuel tank, rereading this thread, you've said you're seeing 38 PSI of fuel pressure at the rail (which is correct for a '95). If so, fuel shouldn't be your problem. I didn't see where you verified that you're getting spark. Perhaps I missed it. I also did not see where you ever said which engine you have. As the SOHC wasn't offered until '96, I'm assuming you have the OHV V6.
Typically, if you have fuel, spark and air going into an engine and if everything is arriving at the right time, the engine should run or try to run. The SOHC engine is the exception if the timing chains jump time, but I don't believe we're talking about a SOHC engine in a '95 and it would be quite rare (though not unheard of) for an OHV engine to jump time or break a timing chain.
I don't understand why your fuel pump runs continuously on prime with the key ON. That's not normal, but you're already replaced all the related parts to no avail. I really thought you were on to something with the wet fuel injector and hissing, but replacing the fuel injector didn't help. Other than removing a valve cover, or doing a compression test, I can't think of a way to verify that the valve train is operating. If the camshaft isn't spinning the PCM might only activate the fuel injector on the cylinder(s) which happens to be in the intake stroke and perhaps run the injector continuously because the cam position sensor is telling the PCM that it's time to inject fuel in that cylinder. Have you run a compression test?
