I haven't noticed anything going on with the overflow tank, nothing unusual with the exhaust either. So far I don't see signs of any oil/water contamination. One other thing I forgot to mention... as the gauge approaches 100*C, I can rev the engine up and the gauge lmany times will bump down suddenly. Electrical problem? I did a pressure test today (auto zone will let you take theirs home free with a deposit) and it came out fine. Also just put on a new radiator cap. I am not sure what you mean by "A/C heat and blower on max should get rid of any air pockets" I have done this procedure with the heat on and blower on high. Also I mentioned earlier that the heater will many times start to blow cold? I am not sure if you have considered this in possibly making a diagnosis, but I thought it might be significant. Thank you for any help and any insight you can provide.