The HS screws are spring loaded for the GPU. Just finger tight. Making the screws real tight won't make the HS any tighter on the GPU. Make sure you keep it flat,and alternate the tightening. Go from one to the other alittle at a time to start then diagonal till tight.
Guess no one is really sure then. I read around here some people saying shin etsu others saying AS5. eitherway it was probably a poor job by the company of applying the thermal paste.
It is interesting how a chip that gets 30c hotter than my P4 uses a heatsink that was made for a 486 cpu.