ok guys please bare with me a try to be kind. I am not any sort of mechanic but I am in dire need of help ,thought I might get some help from you guys

ok so this is the deal, we bought a older 90 mazda b2600i pickup for cheap. Just to use as a beater pickup. This is the problem we are having. It's getting way to much fuel. There is a 1/4" gap in the exsaust pipe fitting connection right off of the manifold. Yes needs to be fixed I understand but not the current issue. When the pickup starts it will run and fire up great but after few second it starts dripping fuel yes fuel out of the exhaust pipe on manifold. Then it burst into flames. Yes big problem and very dangerous I understand. Along with these issues we also have fuel in the oil pan😬😬 but like I said other than catching fire pickup runs fine.
Ok this is what we have tried and replaced n hope of solving the issues of the pickup getting to much fuel. Put in new fuel pressure regulator and fuel pressure damper, new fuel injectors. The next step is to try and locate return fuel lines in hopes that one is blocked. Any advice on locating the return lines or know of any diagrams that would be helpful. Could this issue possibly be from a fault fuel pump or a bad 02 sensor. So sorry for the lack of knowledge but any help would be great. Like I said w bought this as a beater pickup and don't want t send it to a mechanic.
Thanks for any help.