According to both the shop manual and owners manual, the 4 speed capacity is 6 pints.
The ratios on that trans are; 1st gear-7.06:1, 2nd- 3.58:1, 3rd- 1.71:1, 4th- 1:1, Reverse- 6.78:1. Couple that with the 4.56:1 ratio in the differential, it makes the first virtually unusable for anything other than getting a load moving, and second isn't much better.
On the lack of power issue, before you go digging in the feul system, you may consider checking the timing.
