High RPM Backfiring...

I had a close call the other day where I had to get in the gas to get out of it so I rammed the gas and hit about 5K rpm. When it hit 5K, it started
backfiring rapidly and i had to get off the gas b4 it shifted into 2nd gear. I had a friend tell me it was probably a timing problem so I took it to the dealer and they told me it was my rev limiter, that everything was fine. I still didn't like the sound of it, shouldn't it have shifted b4 hitting the limiter? It seemed as if it wasn't going to shift until i let up on the pedal. If this is the case, what can I do to have it re programmed to shift at 4500K rpm or so without spending $500 on a programmer? Would this be something a shop/dealer can do for cheap? Other than that, everything seems fine. Thanx in advance for any advice.
1999 Chevy Silverado K1500 Z71 5300 Vortec, 68K mi.
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Something else has to be going on. 5000 rpm`s is not alot. For some reason the computer is saying your way to high. I have a friend with a 2000. I`ll ask him what he thinks.
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