I'd suspect vacuum leaks before anything else. A d-jet system
tends to run rich when it gets old (the diaphrams crack or the
injectors leak or the sensor wires get shorted).

Running lean is kinda odd.

Of course, I have no direct experience with d-jet except that
I kinda understand how it works and I've monkied with plenty of
salvage yard motors, but then they've *always* had their plugs
as fouled and black as can be. I've yet to see a d-jet car with
plugs anything but midnight black and crusty.
chris