Sean's (& Ed's & Scott's) Astor GTi6

[cully]

have you refitted the ptfe gasket more than once?

if you have the ptfe gasket can only be used once as it is a crush type gasket it crushes and molds to the manifold/head shapes
and once crushed wont re crush to take up any imperfections again

we use ptfe sheets to cut gaskets for steam flanges once a 3mm sheet is crushed in the flanges on removal it can be as thin as paper so it a throw away item not reusable