I have magnetic sump plugs fitted to the TF160 in the sump and the gearbox.
The gearbox has a built in magnet anyway to catch the iron fillings, but an extra one never hurts. Last time I did an oil change there were very fine bits of metal stuck to the sump plug. Not enough to worry about, but they are not in their now.
These are the ones I fitted:
and this was the sump one on the last oil change:
This is the one. http://shop.motorsport-developments.co.uk/m14-x-15-magnetic-oil-sump-drain-plug-343-p.asp