Ford 445. . .fuel starved?

1) been running a mixture of filtered waste
vegetable oil and regular diesel.

2) tractor got to running rough, swapped out fuel
filter (really needed it)

3) tractor ran fine. . .for a couple hours.

Currently: tractor busts right off. . .starts
right up. If it has been setting for awhile, it
runs quite smoothly for 45 seconds to 1 minute,
then starts "popping" and loses power.

After a few minutes, the throttle doesn't change
the engine speed, power drops off to almost
nothing, and eventually she'll die.

It will start right up again, run (albiet while
popping) for another few minutes, and repeat the
whole process.

I've blown out the lines, I've replaced the return
fuel line that was leaking, and checked the
injector lines for leaks.

When the tractor is running smoothly, a steady
stream of fuel comes from the return fuel line. .
.as the tractor loses power, that stream
disappears.

It looks to blow grey/dark smoke when it starts
messing up.

Both air filters are new (2 months/10 hours old).

Antifreeze is full and green. . .none in the oil,
either.

I hope that is enough info for *somebody* to point
me in the right direction!

It does sound like it's lacking fuel, although the dark smoke sounds more like a rich condition (restricted air). Have you taken the tap out of the bottom of the fuel tank? There is (or is supposed to be) a screen there, that may be plugged. It may be that there is enough sludge in your tank that it will run a bit, then the screen can't let enough fuel through to keep up with demand. I've had this happen to two tractors that I've had. The bad filter would point to contaminated fuel as well.

Clean and flush tank of all the wax... get all filters and screens clean. then run a really good injector cleaner through it.

Cleaned/flushed everything last night. Tonight I"ll
put it back together, dump some cleaner in, and see
what happens.