NEW YS-110 idle attitude problems...

The engine its mounted inverted with the tank at the CG, it can be adjusted to idle around 2500 RPM's with no problems; you can maintain it idle the whole tank if you want.

The problem comes when you change the attitude of the plane; if you put the plane nose up or inverted it would accelerate and then die (lean), if you go nose down it will just die (rich).

The symptoms look like an under pressurized system, so I check the pressure built in the tank and it seems poor to me, so after checking for any possible pressure leak(every thing was OK; I tried four different check valves 2-YS, 1-Tettra and 1-Cline

YS and Tettra: same result poor pressure.
Cline: The engine was not able to pressurize the tank, the pressure coming from the engine was not enough to open the valve.

I check the fuel pump ducts and the silicone gasket for any leak or obstruction; nothing found.

Could it be a misalignment or defect on the disk valve?
Any other suggestions???

Thanks,
Joaquin