truck bogging down help plz

[rooster76]

07 sierra 4.3 truck will drive OK for a little bit then it just falls on its face have no acceleration at all and slows down when going up a hill and if I give it half throttle or more it pings bad. It sounds like it it muffled really bad. I have no clue what else to do.
I have changed coil,ICM,plugs, plug wires, rotor and distributor.
Never ran into this problem before plz help

 

[Molson02536]

07 sierra 4.3 truck will drive OK for a little bit then it just falls on its face have no acceleration at all and slows down when going up a hill and if I give it half throttle or more it pings bad. It sounds like it it muffled really bad. I have no clue what else to do.
I have changed coil,ICM,plugs, plug wires, rotor and distributor.
Never ran into this problem before plz help

Check to make sure your Catalytic converter has not gone bad and is restricting the flow of your exhaust.

Start with that and post back your results

Molson02536