[ngoma]

Agreed that compression test results that show consistent readings balanced across all cylinders is more important that the actual numbers, given that at this stage we can consider the engine not even broken in yet (you did replace the rings and rehone?) and the actual compression should rise during complete break in.

As far as troubleshooting the IP, this is where you start swapping injectors to see if the problem follows the injector or not. One recent poster successfully used that method to find the issue to be one IP delivery valve missing its spring. But in your case the previous test (removing fuel to each injector sequentially) results were rather nebulous so we might start looking at more esoteric causes.

It is possible to reassemble the IP with the internals 180deg. out, but you said the IP was rebuilt by a reputable shop?

Possible that the throttle lever could have been removed and replaced in a different position on the splined shaft? Known to cause idle and off-idle issues.

More troubleshooting perception aids:

No-contact IR thermometer to measure temperatures at exhaust ports (better than your fingers!).

Mechanic's stethoscope (or hose, or long screwdriver, etc.) held at each exhaust port, and each injector boss, to help discern any audible differences between cylinders.