You wouldn't happen to be english, would you? After the UK ban on leaded gas and its associated high octane ("4 star" as they call it) Volvo itself suggested lowering the compression by putting in 2 head gaskets better to handle the ubiquitous "euro" (95 octane unleaded, the most common gas, roughly equivalent to 86 octane in the USA). Personally I think it's proof that Volvo has a "nocturnal aviation engineering" (ie. fly-by-night tinkering) division stashed away somewhere without telling the rest of us merry tinkerers.

I think it's one of the less brilliant ideas to come out of Gothenburg, on par with the biodegradable engine harnesses and the PRV-6 we all know and love. Gaskets are designed to be firmly sandwiched between two strong metal mating surfaces. Sandwiching them to each other will increase the risk of leaks, screw up the torque numbers on the head bolts, and is just messy engineering.

Sure, if you want to play around, go ahead. It'll probably work for a while at least, you may get lucky and have it last, but it's not something I'ld recommend for general deployment.

Bram