I got a PTC 9.5 inch 3,500 stall from Dusty Bradford for sale that shows 4% slippage, If you want it you can have it for $900.00 I paid $1,200 when new, this one has the 17 blade sprags, really nice convertor, I am going to lock up and a little tighter as my car sees mostly street duty. let me know, and yes PTC convertor is money well spend all day long.
I have not dyno tune my GN yet but I have heard of CPR in Gardena and Church Automotive Tuning in Wilmington ( My friend tuned a Honda but they tune all makes/models)