possible answer
I had similar problems with converters way back when I first started running NOS. What I had gotten to the point of doing is not recommended by most but I found effective, Jack the ride up and run the engine with tranny in high gear. Get it up to a temp of like 140 or so and record what the engine temp and run time was, then pull the 2 step chip out bring it up and see where the "dead stall" is at on the converter. Write these numbers down in your little black book. The later down the road if you suspect converter problems go back and repeat the test and compare notes...
Not saying this is the right way but it works for me. Now I can just read my data logger, but when I put in a new converter I always do it like that. I will even be doing it with the new billet bolt together I'm getting from chance next week or 2
Scott