I bought a manufactured home with two bathrooms. Both bathrooms have Mansfield 160s. The main bathroom has its original Hardware and flushes fine. In the master bathroom the hardware in the tank has been replaced with fluid master flush valve and fill valve. When you flush the tank empty completely the bowl fills up to the rim and then goes down slowly. If I put a plunger in the bottom of the bowl to block the toilet, flush the toilet till the bowl fills and remove the plunger the bowl will empty with a WOOSH. What could be causing the problem?