terry gt

Here is a solution for you , search 16v performance

danglerb

US has catalytic converters, Euro doesn't, as far as I know that's 100% of the difference.

Euro in the US is supposed to be federalized, cats added and various other bits, so its likely making less power than the same year US model setup from the factory to meet US standards.

slate blue

If you take this one step further the 944 head is the clear winner. Regarding the valve spacing, the 944 head has it's exhaust valve approx 3.5 mm closer to the bore (relative) this means if you go to the trouble of then moving the intake to have the same spacing as the 928 you have then corrected a bore shrouding issue that is present with the 928 head.

So with the modified 944 head you have unshrouded the intake from the bore by 3.5 mm. That is very important for flow and the exhaust valve just in case some are wondering doesn't need anywhere as much clearance from the bore. These engines can make really good power when the factory parts are optimized and then mated to a really good exhaust. Preferably with a bypass valve.

slate blue

Absolutely, it just needs to be properly checked and I don't think anybody has done that yet. This offset is the reason the early cams wear on one edge only.