Rx4fun

The '88 is not running on days that are 90 degrees or hotter. The ride starts out fine, then the car shuts down as if vapor locked. (not supposed to happen with fuel injection) I have replaced the ignition control module,(AC Delco) the cap and rotor, filled with top tier gas,(chevron 96 octane) checked that the fuel tank is venting correctly, have pulse at the injectors, fuel pressure 34 psi at the rail when running, and there is spark when turning over. Let the car sit and cool long enough and starts. Not sure what to pursue next. I am thinking pick up coil, fuel pump relay, or the fuel pump itself. The problem seems to be happening when the fuel tank is below 1/2 full. Any advice will be appreciated.