[weebyf15]

Hello; I have a 1979 P337 and just had a new vacuum pump installed on the rear engine. However the suction is reading only about 3 versus around 4.8. Somebody (Cessna?) has hidden the relief valve somewhere that my mechanic and I can't find. Does anyone know where the rear suction relief valve is on a Pressurized 337 is located?
Thanks