[Adger Smith]

Do an A-B-A test of the manifold change at the track to check that out.
The 1.96 you are talking about probably uses the heavier V8 planetary.
Could the original owner be mistaken and had a 1.98 that is the lite weight 6 cylinder planetary?
There is a substantial weight difference, I'm talking major lbs...
It takes some time and HP to get that heavy planetary moving.
The 1.98 also has one of the best % drop in shift RPM of all the aftermarket ratios. Anything lower than a 1.98 has more than a 50% drop in RPM and becomes power and weight as well as converter sensitive. Just the difference in (both trans were tricked out with lt weight parts) the 1.76 & a1.98 in my 3175 lb 660 HP Camaro was almost .25 sec.