DarkMagician

I am experiencing a loud crackling noise coming from my exhaust manifold on the right side of my engine, it has never done this before and wondering if anyone has advice or information regarding this issue. It is a 93 Ford Mustang with 2.3 NA and has 85K original miles. The noise started when I had drove the car to the store and parked it, when I came outside to leave (it was 20 degrees outside) and I accidentally flooded the fuel injection system and it started rough and started making the noise ever since that morning. The noise worsens when it rains or when it's very humid out. Also, it will go away when certain fuel is used; I only use premium 93 OCT fuel, but I also use 100% gasoline and it goes away. I have tried 12 different fuel system cleaners and I use Marvel Mystery Oil at every fill-up which my car runs smoothly on most of the time, I use Marvel Mystery Oil as a upper cylinder lubricant. For instance I can use Lucas Octane booster and shell 93 premium and it will make worse noise, and if I use Marvel Mystery Oil with 100% gasoline, the noise is almost not there at all. The noise isn't present at idle, I've hot soaked it with Seafoam, I've cleaned throttle body and K&N filter, and when it rains heavy it honestly sounds like a high pitched rod knock (my engine isn't rod knocking). Just asking for a diagnostics before I take it the mechanic because of price, I prefer to do my own mechanics, and I trust and love the Mustang forums as a great big family.

Coosawjack

Sounds like flooding it might have broken the media in a catalytic converter?? Can you listen to the cats with a stethoscope or even a broom handle if that's all you have??