Good question...
I rarely run WOT, when I'm pulling my camper so times I do, like on entrance ramps. My assumption is that since the H. P. & torque curve start fizzling out about 2,850 or so, its probably best to shift just after that. Maybe about 3,000 rpm. The next big factor to know (after knowing where the h. p. and torque fizzle out) is what r. p. m. you wind up at when you shift. If you shift @ 3,000 and wind up at about 2,100 - 2,300, IMHO that's about as good as you could do. Of course this may vary down the rpm scale if your talking about a 12V motor (since 12V's make their power a little lower) or some highly modified ISB.
- JyRO