Still Need Help

The Guac has been down since January, but I have little time to troubleshoot. So in troubleshooting time, I`ve spent maybe a week on it.

I`ve isolated things (I think).

Symptoms:
Idles from cold start at least 30 minutes (I figure any longer was pointless)
If revved to 2k rpm and held, will only last 45 seconds or so.
- When it cuts out the tach drops to zero
- There are no warning signs leading up to this
- I can repeat this over and over. So it`s not (or no longer) intermittent

Wiring has been checked and re-checked and re-re-checked. Coil
replaced. I`ve now swapped out 3 different coils and get the same
results. Points and condensor replaced. Distributor replaced. I even
put a compufire on it. Exact same results. Wire wiggling does nothing.

Vacuum leaks have all been sealed. The last one was yesterday, a fuel
injector seal wasn`t seated properly which was probably from previous
troubleshooting. (Yes, I got the rear drum loose. The hammer blows did
it.)

Several dual relays tried. Injectors spray nicely when triggered,
don`t leak when off.

Fuel pressure stays up. When idling and warm the vac is between 14 and
15, which is probably good for Colorado.

The only things I haven`t tried are replacing are the engine (heh),
the resistor pack, and the computer.

I`m leaning toward either computer or ignition due to the way the tach
just flatlines like that. Though I can`t see how the computer would
affect the ignition?

Any thoughts? Things I haven`t tried? Help?