I put the transgo in mine, with 3.27 gears, and it made a BIG impovement. I recommend calling transgo about what you should go with, since you have the 3.73s, they have great tech. With the transgo, at 1/8th throttle like you mention, mine shifts
1-2 2800 rpm
2-3 3000 rpm
3-4 2900 rpm...