they're talking about the head warping. The head is aluminum and when heat is applied to it, over time it warps... meaning it doesn't stay flat against the block any longer.. My suggestion for you would be to change the fans out before you do the head gasket. If you're cooling system all looks good, and you change the thermostat and it still overheats... the fans are your next bet. I changed my head gasket..( ARP head studs, cometic 4 layer headgasket) and the car still over heated.. It turned out the be the fans. I had aftermarket fans to begin with because of the turbo. I would recommend the flex-a-lite dual fan with the shroud.
http://www.phantasmusa.com/fal325.html

it shows the yellow, but you can get it in different colors including black. Its what cured my over heating problems. If you need help wiring it if you decide to get it let me know. Good luck brother hope that helps

 

id only go with a cometic or mitsu oem, and most people only need the oem