This subject has come up numerous times on this board and I wanted to help support a 'myth'. Myself and others in the above numerous posts have had a sudden onset multiple random cylinder misfire (P0300) ONLY in closed loop and questioned why people suggested checking wires for such a problem. On a scanner my engine was missing on ALL cylinders except for one, and again only in closed loop as many others had. Knowing this I ruled out wires as the problem, some said it cant be wires, others said it could be but could not comment as to how one bad wire could suddently cause all cylinders to start missing, and only in closed loop. Well, I found a bad wire. One bad wire. And after replacing it the problem is gone. I did not change any thing else, left the coil, O2 sensors, IAT etc alone, I ONLY changed the wires. So this myth is now proven for future reference. I'm not saying this is the problem everyone else was having because certainly others have fixed theirs by changing the above and other sensors. Like I said before I think there is just an inherent instability in the LT1 electrical system, one sensor or one wire goes bad and everyone gets the same problem, multiple random cylinder misfire. ???