car tuned now it runs like shit?

[FattyBoomBatty]

Well if it fixed for a while, I'd say that's it and you just need to replace more of the wires. Cut back until you can find mostly non-corroded wires, then replace them all the way to that sensor. When I disected my 1990 1G harness to modify to fit in my quest, sometimes it was hard to find good wire. Since it's in a hot-ass engine bay for most of it's life it's easy for the wires to become difficult to hold solder.