How to break in a new fuel injected engine?

You're right.... I was thinking only of the flat tappet cam world for the cam break-in part. So probably a non-issue... depending on what cam type the OP is using.

But I'd expect a stock FI ECU with low/erratic manifold pressure around idle and at low RPM part throttle, due to any largish cam, is gonna misadjust the mixture. And an unknown new FI map is anyone's guess. That's the issue, as I understand it.