when i switch from the front tank to the rear tank,the engine runs very rough coughing and and sputtering as though the fuel is not being picked from the rear tank smoothly .
Does it continue to run poorly as long as you have the rear tank selected? Or does this happen just briefly, during the tank to tank transition?
Sounds like valve itself is slow, does it happen switching the other way rear to front tank?. Fuel pump may be failing so a pressure test might be in order, plus be sure the filter is fresh though it would not cause one tank to sputter but both, ya just don’t need to add any restriction. A kink in the tank line might be present. Up on the top of the tank it is hard to see but you can feel it. The line is flexible and easy to kink it on install. It all sounds like it is having trouble until it is up to pressure…