Turning on Stock Internal Amp?

[Looney_Tuner]

hey i just recently bought a 1994 chevy silverado, and once before i had seen directions on turning on the stock internal amplifier in the radio. does anyone have these? apparently from 92 to 96 or something gm had amplifiers built into the radio that were never enabled. there are a specific sequence of buttons, or hitting 2 buttons at the same time that turns it on.

 

i work at a gmc/cadillac dealership and i cant find it through gm

 

any help would be appreciated