Anyone have any knowledge about propane vaporise rs . I have customer with problems.

Claims that it is the propane I am selling him. He is only a small portion of the Propane I sell for forklift use. Had stain test done with supply . It was normal. My belief is that it is with the new emission systems in these toyota forklifts. Claims there is a tar buildup in the vaporiser. Seems to occur only in the new toyota forklifts.