As I've been saying, I bought an EFI kit from Affordable Fuel Injection guys.
Their kit is essentially the same as another, well known kit, that is CARB compatible for those CA residents.
the AFI kit cost, delivered, was just over $900.
My son in law just purchased that "other" kit for a Ford 300 cu in straight six, at a cost of a little over $1,600.
As far as I can tell, both kits are the same...same ECM, same sensors, very similar wiring harnesses, etc.

Well, he spent the last 3 days trying to get that "other" kit to run that Ford engine. No idle, backfiring, rough running (if running at all).
Checked every sensor, connection, looked for possible vacuum leaks, you guys know the drill. We found no problems, had no codes.
As luck would have it, my AFI kit arrived yesterday.
This morning we swapped in my ECM, with whatever chip the AFI guys supplied that was tailored to my slightly modified Jeep 258.
With my ECM and chip, his Ford engine ran perfectly!! We then swapped my chip (or is it PROM?) into his ECM, no go.

So, bottom line, his $1,600+ kit was delivered with a bad ECM. My "bargain" priced kit seems even more of a bargain to me now.
And, with just that little time working with this stuff, and reading the pages here, I feel pretty comfortable with the TBI stuff.
Anyway, just thought I'd share my experience, in case anyone else is running into a similar issue.