01 5.3L. Having a problem with the ole 5.3. During normal throttle and acceleration it is perfectly fine. When i put a load on the motor all hell breaks loose. It starts making a ticking/knocking sound at 3600rpms all the way to 6000. it doesnt sound good at all, and really doesnt go anywhere. It just started doing it out of nowhere, for no reason at all. the motor only has 21,000 miles on it. It seems to be faster with half to 3/4 throttle than at full. Im stumped, so some help would be nice.