[Adger Smith]

That last post brought up a memory of a customer problem.
He had a major converter trashing.
Put the same part# and brand converter back in it and it was slow.
Like the OP is experiencing.
Finally found the Stator support tube that presses in the front pump had slipped and restricted a hole or two.
An aftermarket stator support aligned properly brought back his good numbers.
Just food for thought...