The fuel system will only deliver to the limit of the most restrictive component. Are you using a low-speed setting on the filling station's pump? I always fill complex fuel systems with the fill pump set at about 1/3 of it's capacity or lower.

On my UltraFlash with a main and twin saddle tanks, I used 3/16" vent lines on the saddles and a 3/16" vent fitting on the vent outlet. I drilled out the vent outlet fitting a bit. I also used larger brass tubing in the saddle tanks' fuel stoppers with 3/16" tygon back to the main tank. Then at the main tank, I used the larger brass tubing in its stopper with 6MM festo line to the fuel pump. I can't remember if I used a barbed reducing fitting to 4mm just before the pump or not. Also, I always use BVM Large Clunks and 3/16" tygon with a short brass tube inside each tank. The wrong Clunks can be restrictive too.

Before I did he above, the P140 would not spool up fully. Once I made the above fuel system changes the P140 would spool up to full RPM. To test the system run the turbine at full speed for 20 seconds or so. But if your filling station,s pump is pressurizing the system at a low speed, you have excessive restriction.