I have a 99 Chev. with a 5.3 in it. It's got 260k miles which I know is alot, but I got the pickup cheap and it works great for the everyday running around and hauling this or that. Anyways, I bought it last fall, and it had great power. Ran great and had excellent response. Now just a few weeks ago, I tried to do a brakestand, which before has never been an issue, and it wouldn't even begin to turn the tire over. It goes to 1500 RPM and stays there, if you let off the pedal back to about 1/4 throttle, the motor speeds up to just around 1800. It's got new plugs and wires, new fuel filter, new fuel pump just after I bought it, and a good air filter in it. I'm just boggled as to how this thing could've had such great power and response, and just all the sudden it's like I got a v6 in a full size pickup. Anyone got any guesses?? I was thinking maybe the cats are partially plugged up but I don't know..