2->3 and 3->4 won't shift hard
 

I've got a stock (afaik) 4L60e in my '99 Tahoe 2WD, 2 door, 5.7 Vortec. Using Tuner Cat, I've been toying with Normal Base Shift Pressure vs. Torque vs. Shift and have been able to manipulate the hardness of shifts quite a lot on the 1->2 shift. The attached graph shows the "whiplash" version of that shift... but no matter how much pressure I apply to the subsequent upshifts, they don't seem to get much more firm... impossible to get a chirp out of the tires on those shifts (maybe it's because the Tahoe weighs a few zillion tons and I've got big meats underneath, but I'd still expect a hard shift). Note, that I've tailed off the curves at 190 psi based on discussion threads about max pressure capacity for the stock pump.

Any suggestions? Am I asking for more than the stock unit can do? BTW, I'm not launching this thing from streetlight to streetlight. Just driving it to and from work, mostly highway, but I want extra-firm shifts.