Where you using lube when you broke that tap?
Yup, always do. It felt like it caught on something just before breaking, though I have no idea what. Not that it would take much force; the tap was for a 4mm hole.
I may have a handle on things now though. I was able to drill out the area around the tap without wrecking the TPS's mounting post and extract the little beast. I'm filling the crater with JB weld at the moment and inserting a heli-coil for good measure. I don't see why it won't do the trick; the only force it has to withstand is that of the TPS's return spring.
In any case if it fails, I'm sure someone above will hear from me.
Thanks guys!