doubt that this helps, but as far as the ground wire for the ecu issue goes... there should be just one, atleast on a 90. with out that grounded my car had problems before.

Man I never heard so much whining...

It IS typical for fuel pressure to fall off after the engine is turned off. Some go down to a certain level while others go all the way back down to zero. The real issue is how fast it leaks down. The fuel pressure drop should take a few minutes normally. If it is within a couple seconds then that when you know something is in need of attention.

You can locate the fuel pressure leak, by clamping off your feed line to make sure it's not the fuel pump. Then clamp off the return line to make sure it's not the regulator. with both clamped off and the fuel pressure still dropping your either going to have a fuel leak some where at the fuel rail or the injectors.

If one 780 injector is sticking open though...you won't hold fuel pressure for ANY length of time. that biatch will empty your fuel rail in a heart beat.