Well, here's something for ya.
I had a P4 w/ a semi-mirrored Maze 3. I was using way too much AS3. So, I removed the block and used a credit card to scrape away any excess AS3, and the tested things out. Well, temps were a few degrees worse. Not only that, but as soon as the CPU had any load, the temps shot up, and as soon as it started idling, the temps fell quickly.
So, I took everything apart, and looked at the chip. The built in heat spreader was not flat... not even close. It was high around the edges, and a little high in the center. So I lapped it. I tried 600 grit, the 400, and finally 320 started helping. It was waaay off. FYI, the heat spreader is made of copper. I don't know what Intel did to make it silvery, (aluminum perhaps), but now its fairly shiny copper, and flat.
I put things back together, and a used a Kleenex to daub on AS3... a veeery thin coat, on both the CPU and the WB. I worked the WB around to get everything to settle in, and then cranked the springs down all the way.
*Temps haven't changed a bit. Maybe just a tad higher, but it feels warmish in this room, so who knows. Maybe I'll add more AS3... maybe I'll take it all off. I dunno. I only used enough this time to make it look a little silvery. hmmm. If nothing else, I probably voided my warranty. All is not lost.