Went from stock d5 converter to the art Carr. My previous best time of 12.28@115 was before the transmission rebuild. Apparently you usually lose mph when going to a NLU converter.
I'm not real happy with the mph drop. But from what I've been told with the loose art Carr converter you give up mph for 60 foot and faster turbo spool.
Running 25 then and now.. Before I couldn't hold any boost. I installed s10 wheel cylinders and can hold 10 easy. Before converter change I was running 8.xx 1/8 at 91 mph. With the art Carr I'm running 90 mph at 7.4. I wouldn't be getting 1.6 60 foot with the d5. So I did lose mph last 1/8th but have gained a lot in the 60 foot.
Ya, it looks like your converter is not coupling at the top end. You may want to consult the converter experts here to zero in on something that might allow you better coupling at the top end without giving up too much stall.