So what, exactly, are you posting for? Are you asking how to get manual first?
When I first got my '95 Z28 convertible ( with the 2.73:1 axle, not the 3.23:1 option ) I had to use a hammer and sharpened straight screwdriver to knock a plastic tab off the shifter ( carefully removed the center console first ) to get manual first. That's all it took. And I only did that for winter driving, because with the Hypertech tuner it would hold first to 6200 at full throttle. I liked that.
If you're talking about a pickup, it may well be an electronic thing so that you can't have first above a certain speed. If this is your problem, then you'll need to find a tuner or send your computer out. I used www.gmtuners.com
to recalibrate the speedometer and shift points of my '06 Sierra when I changed the axle ratio. They had the best price and the best service. It cost me much less than buying another Hypertech.