BTW, as for tapping a nipple into the threaded pipe:

Right now, I have a smoke tap on two 4-stroke mufflers. Neither one is on a threaded pipe. However, my newest YS 110 has one of those threaded pipes, and my plan is to grind a flat in the threads and drill there. If that doesn't hold, I'll add some JB weld.

I find it hard to believe that won't work.