I have only started reading on this site, but there's lots of info here on transmissions. Mine problem is a lazy shift at 50% throttle, it may not even be the Modulator, but I will be doing the modulator before going here, for more adventurous DIY's.
I found Trans Test Kits, but they come with a number of different threaded fittings, so still looking for the test port thread. I may have to pull my plug first and measure it myself.
http://********/articles/transmission/k1/
Dan