Back when I had GPASC heads, most likely from EMPI, with the oversize valves, the exhaust seat kept melting into the head. This was before GPASC realized that oversize valves were not necessary. My fix then, was to get genuine VW heads from Brazil with standard size valves. Problem solved. I don't know if they even make them anymore. But I think the real problem was the oversize valves on the exhaust because they cut out too much of the meat of the head around that valve that it could not get the proper cooling.
See N64KR at <http://krbuilder.org/> http://KRBuilder.org - Then click on the pics 2016 KR Gathering - Mt. Vernon, Ill. Peoples Choice at 2013 - KR Gathering in Mt. Vernon, Il - MVN Best KR at 2013 - KR Gathering in Mt. Vernon, Il - MVN Best Interior at 2013 - KR Gathering in Mt. Vernon, Il - MVN Best Paint at 2013 - KR Gathering in Mt. Vernon, Il - MVN Best Firwwall Forward at 2013 - KR Gathering in Mt. Vernon, Il - MVN Best Interior and Panel at 2008 - KR Gathering in Mt. Vernon, Il - MVN Daniel R. Heath - Lexington, SC