oil filter backing plate

Trying to remove an oil filter backing plate from a fresh built motor due to oil leak at the plate. It was well sealed (gasket used), upon fire up it was leaking at the 11 o'clock position. Stock four hole plate (not a 90 deg) and 75 psi oil pressure. Can't seem to remove it from the block to replace the gasket...any guidance out there would be helpful. Special tool to remove the plate?