I seem to have external gas leakage from the injectors. I have removed the rail and replaced all of the o-rings to no avail. I was alarmed to find mixed-type injectors. There are two types (long shroud and cap types) both will work. However, I wonder if intake manifold prefers one or the other. I can't rule out a leaky injector body, but I have at least two that are leaking.

It'* very likely that some of the injectors were replaced at one point in time, perhaps before you bought the car, hence the different style of injectors. I would say it is probably leaky injector bodies beings you have already replaced the o-rings. This is not too uncommon on an injector of this age. They were of poor quality back then compared to the injectors now a days.

Did you happen to test the schrader valve? I've seen a surprising amount of those loose... not too uncommon. The only other leak that could be there is on the lines, you put new o rings on them right?

The only thing left is just replace all injectors. Grab a fuel rail off an LN3 [88-91], very few of these go bad.

Remember, gas is flammable, if you have a leak there, and it goes on your [hot] intake.. that makes fire. Gas leak = parked car.