I'm having the same trouble as Keefer with his tyga pipes,looking at your posts paul you say that you use the thick oem copper gasket with the tyga stub manifold,if this is the case the lip on the stub manifold(which is the same thickness as the oem gasket)would not sit inside the machined part of the cylinder,and it just don't look right to me
Looking on the tyga website no copper gasket is shown on either the exhaust picture page or the 300 kit picture page and the stub manifold is.
Cheers Rob.