Quite common DME relay issue. Specifically no-start when car is warm is classic DME relay problem.

Testing procedure here - if the relay is the issue, I recommend investing in a solid state dme relay from F9tech. Youll never have the problem again.
http://www.clarks-garage.com/shop-manual/fuel-05.htm

I recommend reading through clarks-garage which is a well known source of all sorts of 944 related issues and solutions.

 

Yep. Yep. and Yep...

I did get the FT9 DME with diagnostics and it does not start much better but still has a delay (increase in cranking time) that is linear with time after shutdown so I do think it's a fuel pressure leak (backwards or forwards).

I'll figure it out eventually but the car is running fine and starting performance is now acceptable so just enjoying it.

Thanks.