I just glanced at the thread but it seems from reading that you are only having issues at low speed/idle?
If so, please take the time to read through my thread and all the different things I tried to get my car to run cool at idle. It was great at cruise but as soon as I would stop for more than 5 minutes it would start creeping up.
There are a lot of tips in my thread and an eventual fix for my situation. Not sure if yours will be the same but there are likely to be things you can try if you have not already.
http://www.chevelles.com/forums/show...474&highlight=
If you can spend the $40 to try the same fan I did, it might be worth your time. I took the car out yesterday and with my new gauge I could watch the water temps fluctuate from 160 to 164 and back.