You will always have metal in the bottom of the pan, how much, well, that is the question. The debris is what the flush gets out better than the drain and fill, limiting the build up.

The isuzu autos are mostly interchangeable. Their are a few not 4l30's on the 02 or 04 rodeos and axioms, I forget the year break, but the rest of the 2nd gen autos are 4l30's.

I think there is a computer issue with switching to a 4l60, but not positive about that. If it was a direct swap, a lot more people would be running them.