I have a 2003 GMC Envoy. A couple of months ago I noticed I would press my gas pedal and it would be slow to get power. Its gotten worse now. I'll slow down and go to accelerate and the truck just smoothly rolls like its coming to a stop. I'll have to press the gas over and over again and it eventually moves. While I am pressing the gas the RPM is not moving. When the truck finally does jerk into motion thats when the RPM needle moves. There is no code showing. I've even taken it into Autozone and had them try to find a code but they don't show anything as well. This is getting to be very scary cause I feel eventually the truck will just finally come to a stop in the middle of traffic. I won't even get on the expressway anymore. We have statrted with the cheapest fix of changing the gas filter but that hasn't helped. Any suggestions? The truck is 2003 6 cylinder 4.2L engine S