PorscheDoc

pull the line back to where it goes over the torsion bar carrier, and just cap it there with a one way check valve. The valve will keep anything from going out.

samluke

I found that the vacuum operated valve (valve J)was leaking. I opened it up and found the diaphragm had aslight tear. I changed the fuel tank vent system, eliminated the boost and vacuum line. I vented the tank through the carbon cannister, it seemed open. I can now see how boost air was getting back to the tank, just not sure why it was getting locked in and not venting.

I also stiffened the stock tranny mount.

Drove the car for an hour or so (obviously not in race conditions), no hint of any pressure in the tank.

Hopefully problem solved, I'll monitor it the next time I'm at the track.