Just this year after the winter, the engine will not tach up to the normal 5800 - 6000 RPM's. I have run a can of OMC Engine Tuner through the engine and replaced spark plugs with no favorable results. The commpression is around 100 psi on all six cylinders. Engine also has problems idling and the power to sometimes load on trailer. I was thinking that maybe it's time to have the carbs rebuildt. Help!!!