Poor hot idle caused by ethanol gas? Whaddya think?

I have a similar problem on my Australian built AP5 Valiant. I have changed the ECG valve. plugs points Put a kit through the carby, changed the manifold gasket. Checked all of the vacuum hoses. Runs fine at start up. Shut it down after about 10 miles restart it and it just doesnt want to idle. It seems to be sucking air from somewhere but I have no idea from where.