I'm sporting them as well.
Miles...don't know for sure...been about 3-4 years now I guess. I have reused them once already when I did a tear down and replaced my piston rings with file to fit rings.
How much boost? I'd say 10-11 PSI on my GenV easy.
Sporting the MLS head gaskets as well. On the fist build, they went in dry out of the package. I reused them as well, and didn't want to take chances with that, so used copper spray the second time around. Still fine to this day.
Side notes/personal opinions:
If your building an engine - buy them!
If your installing "worked" heads - buy them!
They are money well spent for the fact they are reusable, and pretty much bomb proof.
Need tips on installing them, trouble and worry free? I would be happy to help you out with all the little tricks of the trade.
~F~
