I'll throw in my 2 cents here.
I was making 320rwhp BEFORE a smaller pulley on the Vortech, headers and 2.5 inch exhaust. Don't know what I'm making now but I bet it's a fair bit above 350rwhp, possibly getting to 400. Need to re-dyno I guess.
Anyway, I've made 70+ 1/8 and 1/4 passes and so far so good. Current best 1/8 time is 8.285 which should be a flat 12.8 or less. The only problem I have is that I bounce on the rev limiter during the 1-2 shift at WOT. I'm not really convinced it's a trans problem. I think it's either the solenoids or an ECU control issue.
Also, it's very easy to do some mods to the box. At very least, the base line pressure can be raised by tightening the throttle valve cable. It's also possible to adjust the main pressure regulator, all you need to do is drop the pan and turn it.
Shimming the accumulators is also a good thing, shorter shift time = less transmisison wear. This does require droping the valve body but it's not by any means a difficult task.
KC