ENG PROBLEM CAUSED TEST ACFT TO LOSE ALT. LOW FLT OVER POPULATED AREA.

Narrative

I WAS FLYING MY EXPERIMENTAL ACFT; IN CLR VFR WX ON A TEST FLT IN THE LCL AREA. I DEPARTED MATHIS FIELD (SAN ANGELO'S ARPT) AND LEFT THE ARPT AREA TO THE W. AFTER DOING SOME MANEUVERING W OF THE ARPT AREA; I HEADED E; XING OVER THE FAR S END OF THE CITY; ABOUT 10 MI N OF THE ARPT. I WAS CLBING FROM AN ALT OF 2700 FT WHILE I WAS MANEUVERING W OF THE ARPT TO 5500 FT WHILE HDG E. AS I WAS XING THE S END OF SAN ANGELO; I STARTED TO LOSE ENG RPM AND ALT. I CONTINUED TO FLY STRAIGHT AND LEVEL (E) WHILE I SURMISED THE SITUATION. MY FUEL PRESSURE GAUGE INDICATED THAT I WAS LOSING FUEL PRESSURE AND WAS NOW DOWN TO 0.5 PSI WHICH WOULD ONLY MAINTAIN ABOUT 3000 ENG RPM. I WAS IN A SLOW CTLED DSCNT WITH THIS PARTIAL PWR; AND AT AN ALT OF AROUND 2400 FT (ABOUT 600 FT AGL) THEN I INITIATED A 180 DEG TURN BACK TO THE W AND AWAY FROM THE CITY. DURING THIS TIME I WAS TRYING TO INCREASE FUEL PRESSURE BY TURNING ON MY AUX FUEL PUMP AND SWITCHING TANKS. MY FUEL PRESSURE INCREASED AS I SWITCHED FROM MY MAIN TANK TO THE WING TANK AND I WAS ABLE TO INCREASE ENG RPM TO FULL (6500 RPM) AND START CLBING AGAIN. I FLEW ON TO DUCOTE FIELD; AN UNCTLED PRIVATE AIR PARK SOME 10 MI W OF MATHIS FIELD; AND LANDED IMMEDIATELY. A PIECE OF SILICONE SEALANT WAS STUCK IN THE SELECTOR VALVE INLET FROM THE MAIN TANK CAUSING THE FUEL FLOW PROBLEM. THIS WAS EASILY REMOVED AND I RETURNED TO MATHIS FIELD AND MY HANGAR WITHOUT INCIDENT. I AM SUBMITTING THIS RPT TO DOCUMENT MY DSCNT AND TURN OVER THE S SUBURBS OF SAN ANGELO.