Hi, I own a 2002 trailblazer 4.2 4x4 that has really poor acceleration and power. I have changed plugs, o2 sensor(upstream), air filter, fuel filter, oil, & transmission filter. Also put some fuel system cleaner in my last fill up. When I changed the plugs I decided to clean the throttle body. I read somewhere that with electronic throttle bodies not to manually move the butterfly. So, I turned the key on (didn't start engine) and put a big brick on the gas petal. The butterfly barely opened at all. Also heard a quiet high pitch tone or like beep sound coming from the throttle body. My question is shouldn't the butterfly open further? I assumed it would open all the way. Mine barely moved maybe 1/2 to 1 inch of movement. Also when I took the brick off the gas petal I was able to walk around to the front of the vehicle before it closed. As you know the units are expensive. Is this normal or do you think the throttle body is bad? Thanks.