Still Cutting Out At High RPMs. What To Try Next?

What Rick said^^^^^^^^
Have the injs EVER been cleaned/flow tested, that you know of?
Im not sure anything has ever been done with the injectors. They are the stock 28lb injectors. Is there some sort of known problem with the Caspers cam sensor cap?
I have no experience w/ the Casper cap, but I've "messed with" a few injs.:D
The Bosch 218 injs appear to be a lot like a Timex...Takes a beating, and keeps on ticking.
@ 150,000 mi, [and 25 yrs], they could have issues caused by other than the inj.
Bad harness connections.
Dirt from poor maint.
Rusty fuel tank.
Lines that have the inner liner failing.

The injs could have failng coils, corroded pins, rusted internal components.
This design was in production long before ethanol came along. I have no data to support they are/are not compatible w/ that fuel.

The only way to verify their condition is to flow test them.