60' gone away (repost)

I have been wondering about my PTC 9.5 converter. It is embarrassing on how long its been ignored and how old it is. I have made the car better a bit in all ways, but it has not equaled or bettered its best 60’ in years. 1.70 is the best ever, I can get a 1.73 out of it now. I just started logging slip through the run. At the bottom of top gear it is at 10.3% and drops to 3.9 % at the stripe. It flashes to 3300 rpm at the hit and starts to load the motor. The lack of improvement in the 60’ and another car just killing me in the 330 that doesn’t usually that much, makes me wonder. It’s been 10 years and 1000+ runs. The plan is a 904 so don’t want to put money it the 727 converter. The car performs fine, just would expect more pickup in the 60’