I just bought this truck and it was shifting irregularly, the engine seemed to lope and idle high. I used a OBD-1 diagnostic and came up with a few issues. I upgraded the battery to what it called for, changed EGR solenoid, Oxygen sensor and fuel filter. Then, it drove great for one day! I was driving and it would start in what seemed second or third gear. My RPM tach is not working, my speedometer was jumping erratically as was the engine then it would die while moving in gear. So, I figured it was an electrical problem so I started looking. I found my GM_4L80E electrical connector was covered in oil and each wire was exposed and touching. I figured that wasn't good! So, After checking all the junkyards I couldn't find this plug. So, I went on and repaired each one myself! Feeling good about my work I turned it on and it started right up! Put it in gear and it seemed fine. So, I took it around the block and upon each acceleration it would jump three times then mellow out. Plus, my oil pressure gauge was dropping to zero and causing the check gauge to keep popping on. I'm so lost and I need someone who has dealt with this before. What should my next step be? Do I need to upgrade my entire harness or what??? HEEEEEELP!!!!!