Just a few quick notes on your computed figures....
Real world with my 3.45's, 70 MPH equals 2150 RPM. With my tune, the max speed AFM will engage at is set to 72 MPH so that's generally where I run down the Interstate under cruise. With the tune in, the 5-6 shift with WOT takes place at 150 MPH. I'd have to take a look at the stock calibration to see what the 5-6 shift point recalculated to with HP Tuners based on the OEM (non-tuned) settings, shift points are one of the parameters that I believe are automatically recalculated when you change ratios. But yeah, unless you are purpose-built for racing and trailer the car, 95 +% or more of the time you're looking at zero to 90 MPH for max street range of speed daily driving. The 3.45's get you noticeable improvements there without too much impact on fuel economy. I still see 22 MPG average with mixed driving.
It's so very important to run a tune in these computers after you start playing with the ratios to get the most out of your car. GM does traditionally tend to be somewhat conservative, even on a PPV calibration. Ask the guys down at Redline Motorsports in Pompano, Howard and his crew down there have had very good luck tweaking more power with the PC when he does special projects for GM or custom builds for his company's stuff. But, most times you couple tunes with hardware mods anyway so you play with A, you change B.
Oh, I didn't see the earlier question but a little bit of the tweaking is mine, most of it is Chris Henry's tune which is his proprietary sold product. He's the guy we need for this discussion
