Well, the fuel leaking down is going to be a big problem. I would start with this first.
Either the fuel pump check valve has gone bad leaking fuel back into the tank or the fuel pressure regulator is leaking fuel into the engine causing your misfire.
Sorry for the delay!
Is the problem more at idle or under a load? I know that you said that the idle is erratic but is it worse under a load or does it get better? If it still gets better under a load, then I would lean towards a vacuum leak.
Ok... I think a vacuum leak is going to be the problem. But first, I know that you said that the fuel pressure did leak down fairly fast. Did we ever correct this problem? Does the fuel pressure still leak down with the key off?
What is the fuel pressure currently at?
Verify that fuel pressure is going to 60+ PSI with engine loaded, vacuum at 0".