I looked into this some time ago, and it is pretty clear that the poor fabrication quality allows the capacitors to burn internally, increasing the internal resistance. The best options are (1) get one from one of the better manufacturers, like Bosch, if you can find one that fits; (2) replace the usual one with a polypropylene industrial capacitor, which is readily available from Digi-Key or some similar electronics supplier. I use 0.22 microfarads, and about 400 volts is enough; higher voltage is OK. The latter will require a little work mounting it in some way and connecting wires to it.
By the way, I've read that story several times about the capacitor changing value and determining whether it's high or low from the way the points burn, and I can't for the life of me imagine any way that could be valid. I'm VERY surprised to see it in some Toyota service literature. In any case, the value of the capacitance really can't change--it's just a roll of foil wrapped up with some plastic, probably mylar. The electrical properties of the materials won't change, and the size of course won't either. When a capacitance meter shows a change, it's probably being upset by the increased series resistance.