Sucking versus blowing varies from HSF model to model. From my own experiences, I'd say that blowing results in lower HS temps, but can cause case circulation descrepancies. The stronger the blow, the wierder the effect. I don't think that is the problem with your HSF. Also, I'd say the 6035 has adequate capacity for loaded as well as idle CPUs operating in the range yours is. Just because you can get the clips to snap, does not guarantee a foolproof mate between the core and the HSF base surfaces, but it is a good start. Keep seeking, as something is not kosher there.
Hoot