Here's my take on this. First, you didn't say how old or how fresh the engine is, if you did I missed it. The ring seal could be going away. It would be evident that the car runs better when hot.
I don't use a cooler on my race car trans and I leave off a tranzbrake. The car is more consistent without it. Just put a temp gauge in the pan. B, or whatever number we are on, yes you need an extension on the filter