I have the same truck and the 4.3L is horrible when it comes to accelerating. I have the same issue, there just isn't any power. From what I have seen looking around, the 4.3 is more of an engine for an S-10, not a Silverado. The only real solution is to swap for another engine or another truck with a bigger engine. Any Idea where the buzzing sound is coming from? I had a buzzing sound for a while but it turned out to be a shorting out wire in the dash.