First off.. I'm new to the xbox.. but not new in the general sense.
First thing i noticed when I opened up the 360 was the tiny area covered by the exhaust shroud.
Now.. I've been overclocking since overclocking was incepted. So I know heat.
By placing the cpu and gpu next to eachother on the same pcb they were asking for trouble. Cooling them together was a death wish. That area must get WELL over 100 degrees C more than the surrounding board. No wonder xboxes are failing. Traces, pins and solder all have different makeups and thusly expand and contract at different rates. It's not that it's a manufacturing defect.. It's an engineering defect. <<Can't be fixed unless they start using lower power cpu's and gpu's.
And the broken connection is always between the solder and trace, so it's impossible to see.
Heat gun works because it reconnects.. that simple.. but it WILL fail again.
Everybody has bent a piece of metal back and forth till it got easier and easier and then snapped. Thats what's happening to the xboxes.
My advice would be to cut the cover up and give it some real heat sinks with fans or leave it on 24/7 so it can't cycle from hot to cold..
This has prolly been said before.. Just think it's important.