Loss of power but no fuel pump problem indicated from Dynon Data Log
I recently had a 600 rpm drop shortly after take off with my 912ULS. The engine is installed in my RV-12 which I built and have been flying for 5 years (245 hrs). I have done all the 5 year replacement items including fuel hoses,coolant hoses, carb sockets, sending Carburetors off for 200 hr service and 5-Yr rubber replacement, and Carbs balanced. I landed and could not get over 4,400 rpm WOT. Defueled the premium auto fuel and re-fueled with Av fuel. After running the Av fuel for a few minutes I could get the 5,000+ rpm and launched to my home airfield. I had an intermediate stop due to weather. On run up after intermediate stop I could not get over 4,400 rpm WOT. The following day I removed the carb bowls and weighed the floats.Each pair were under 7 grams. Saw not contamination. Installed floats and carb bowls and got 5,000+ rpm. Flew to home base without any further problems. Have flown 4 flights (2.5 hrs tot) within gliding range of AP without problems. I downloaded my Dynon 180 data file which shows an egt temperature difference of over 100 deg to as high as 130 deg for most of the time after the engine rpm drop. The data log for my intermediate flight of 0.9 hr flight after changing to Av gas indicates a more than 100 deg egt temperature difference for 0.56 hrs of the flight. the max temp diff was 195 deg (1,174 Lt/ 1369 Rt).EGT probes installed per plans. Current test flights show less that 85 deg egt temp difference. I have the new fuel pump which I installed less than 2 years ago at 164 hrs. The fuel pressure varied from 4.5 to 5.6 psi for all the flights. Since I have not found a smoking gun I am not sure if my problem has disappeared and I am reluctant to trust the engine. Any comments or suggestions appreciated. Bob Kibby N712BK