82 300d 3 to 4 shift flare.. what is the accum. kit?

I've seen several comments made about an accumulator kit to fix the 3rd to 4th shift flare on the 80 to 83 300Ds. I've adjusted the shift point, vaccum modulator, and the vaccum bleed off points to lower shift vaccum. Still have the flare. Several people have mentioned an accumulator kit for less than $5 but never mentioned the part numbers or a descriptive name to ask the dealership. I just called Ewing ******** and spoke to the parts dept. and an oldtimer on the drive and neither knew anything about a fix for this problem outside of a full overhaul. I kind of expected that. So, if anyone has performed this modification with success, could you forward me the part numbers and a brief description of how it was done. I need to start driving this car relatively soon and hate to burn up the clutches because of this flare.

Best regards,

David