Since this thing got bumped to the top I have a ? for the OP.
Have you had any trouble with the engine running rough at full throttle? I have a buddy who has the same mower, size and engine. His engine is fine when the blade is engaged, but when you turn the blade off and the throttle is full it runs rough. Once you turn the throttle down it is fine. Any idea?
He has put a new fuel filter and air filter and still no luck.