I experienced a similar problem. Replacing the fuel pump relay helped little. Replacing the fuel pump check valves helped some. Replacing the fuel pressure accumulator did nothing. Replacing the injectors helped a lot. I did replace the ignition components first. I checked the air plate static height. It seems to be about 2 or 3 mm below the top of the throat, difinitely not too high (I don't think). I still get the problem rarely when the coolant temp is above 60C and the car has sit for 1 to 2 hours.