Popping at idle on 04 ford f150 4.2l with 209432 on odometer but had rebuilt engine put in 1 yr ago Approximately 2 months ago it started hesitating and stalling upon acceleration then a knocking sound, so I parked it and now it does it while idle and it's rough and occasionally hard start, when you Rev it up the popping somewhat subsides. Plugs are coming out with black soot so I know there is carbon build up. Checked numerous things and replaced coil pack, plugs/wires, knock sensor, IAMC, cleaned EGR, new gaskets on valve and manifold, everything is torqued to correct setting, new air filter and oil was just changed using same filter and oil as always.The popping sound is coming from where manifold and catalytic converter connect. Catalytic converter had busted honeycomb. Did compression test and all good. I've searched and searched but find different answers and solutions. Can it be a vacuum leak? Timing? Injector? I'VE READ SO MUCH ABOUT THIS AND WATCED VIDEOS AND READ COMMENTS SO PLEASE SPARE ME THE SMART *** COMMENTS AND THE SAME STUFF I ALREADY MENTIONED ABOVE….