Small fan on Fuji 4 stage gun

I have been using the Fuji 4 stage for a number of years. It's a grea t investment. Recently, I have sensed that the "spray fan" width is not wi de enough. I then tested with water in the gun; the water is "thin" so it should show the best performance.
I have (again) cleaned all parts of the gun with lacquer thinner. I ty pically have replaced the "air tube/check valve" after each job - even thou gh they seemed to work. The top cap and washers on the cup were recently r eplaced (the new cap is a much better design).
I have ordered more air tubes with check valves to try again. However, the only thing I don't know how to check is the air supply turbine. The f ilter was changed in the recent past and appears to be clean. It appears to deliver enough air.
Anybody go any ideas on what else to look for? Maybe I am "misremembe ring" how big the fan should be. Are there any charts on how big the spray fan should be when using water at 1 foot?
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