This intermittent low fuel pressure "problem" has been an ongoing issue in this forum for many years-just do a search. My 912uls has had this issue since new, and it is NOT a filter issue, sensor issue, vapor lock, or air in the sensor line; believe me, I have carefully eliminated all these possibilities more than once. I believe it is an inherent issue with the newest Rotax fuel pump, but they won't admit it. My engine is on a high wing Kitfox and I do not have any auxiliary electric fuel pump. After 800 hours I finally quit worrying about it because the engine has never even hiccuped during a full power climbout with the pressure below redline.