Gene,
Is something still wrong with the original part of the tree? And did it have borers as well? I would air layer the new growth and get it away from the roots. The new shoot looks very good and healthy.
I have noticed that when my little trees have put out shoots, some of them, as was the case of the Black Celeste, grow faster and stronger than the original tree.
I sawed the Black Celeste in two and the newer shoot took off, but only has leaves at the top of it and the original tree has taken off and has grown well, too, but there was never anything amiss with it, it just looked stunted. Dalton said it would leaf out this season and do well and it has.
noss