DO the poo 4s use a diff tps than 2s?
if not u can build a tps for a poo in about 20min and 10 bucks a radio shack.
I built one a few yrs back just a few alligator clips a 9v battery and a ohm meter is all u need
u can find it on u tube.
the one I built is still working and sitting at a buds shop it is actually surprising how many are not in spec and the owner never knew