2006 Chevy Silverado 1500 5.3

I have replaced calipers, rotors, brakes, hoses and brake
lines. Master cylinder has been checked its good, booster
its good. Booster air flow check valve has not been
replaced. Yet.   The Brakes ate perfectly normal when I
pump it with the truck being turned off. when I turn the
truck on with my foot still on the pedal firmly. The brake
pedal slowly goes down like it should. Once I'm using the
brake pedals a couple times it start locking up. Like a
person driving with two feet... is how it feels.. When I let off
the gas it almost comes to a complete stop. Press on the
gas pedal and it feels like I'm towing a summary.
It was blood the correct way, but someone said something
about resetting the computer. I have never had to do that in
the past after changing out calipers and hoses on this truck
once before. I do a lot of driving down SouthEast through
the mountains.
Now this truck has the towing package on it.  Some parts
we have come to find out our heavy duty & Some are not on
the front end. I know it sounds strange but yes it's true.
PLEASE  IF ANYONE has any suggestions on what it could
be.
2006 Chevy Silverado LT 1500 5.3L, full four door short
bed.