Yesterday after the flight, I checked everything and found nothing amiss. Today, I test flew, but did not climb to the same altitude and temperature as yesterday, and today, everything went perfect, as it has in the past. Yesterday when I got the low fuel pressure reading, I immediately started the electric pump so the engine never had a chance to stumble. Today, with full throttle, at 3,000', I got pressure readings on the Dynon of 3.7 with the mech. pump only, and 4.0 with the elect. back up pump. jAt 1800 rpm, I got 4.6 with the mech. and 5.3 with the elect back up. I think that yesterday, I must have had some moisture that froze in the small, brass screen in my gascolator that caused a partial blockage. I'm open to any thoughts anyone might have. thanks,Bruce