Just a follow up to our discussion.
Got a loaner converter from a member here to try. Advertised 5300 stall, flashes at 5500 in my car and works WAY better all around than the converter I had in the car. Tight in the pits so I'm not revving to the moon to move the car, flashes hard at 5500 rpm, leaves hard and feels fully engaged pulling throughout the run unlike the old one that left like a wet noodle and felt like it was slipping the entire pass. 60' times went from 1.52's to 1.41's so the theory of issue with the converter was validated. 1/4 mile ET went from 10.80's @ 124 to 10.30's @ 130. Still needs more converter just like I thought. 5800-6000 should be perfect.