Hesitating/knocking

My truck listed above is the xlt model. It’s my first vehicle and I am 16. I started experiencing problems with the truck like hesitation once I push on the gas to pull out in front of somebody. Or even trying to pick up speed. After hesitation it slurs and has very exaggerated stutters while being put into acceleration. Rarely will it ever knock, and by that I mean it actually sounds like somebody is hitting the chassis with a sledge hammer over and over. It will also smell like burnt oil within the cab. I have replaced the belt and O2 sensor (knowing this has nothing to do with it), did a tune up, replaced both catalytic converters, and checked it with the “check engine” light on. Please help. I’ve taken it to 3 mechanics and neither know what’s wrong.