Please briefly explain what this theory claims. It might help those from whom you seek information to provide you with relevant and useful answers. It would also help if you would familiarize yourself with the basic structure of turbofan and turbojet engines. Your questions about where the exhaust gases go are a bit strange.
https://www.youtube.com/watch?v=fyAoBI-8Uxg
This theory is everywhere and the only way I can disprove it is by accounting for all the fuel that is supposedly stored in the wings or fuselage of a plane.
(I haven’t had time to watch the link, don’t blame me for whatever is said... I just picked a random one that seemed to account for the white condensation that comes out of the wings... it’s all beyond my pay grade... so again, don’t blame me!)