Some of your problems could be TMCC signal issues.
I couple the TMCC signal to both rails with .1uf capacitors.
If the locos runs better in one direction than the other then you have a signal issue for sure.
You will find that the newer locos may run better and will smoke better if run closer to 18 volts.
Since most smoke elements are 6-8 ohms and use a chopped regulated AC that measures 5-6.5 volts RMS a small increase in the track voltage makes the smoke regulator put out a few tenths of a volt more and that is all it takes to make more smoke.
I was told that they like the "chopped AC" of modern transformers better than old pure sine wave transformer because the peak voltages are higher.
Carl
