Apparently the plastic used in 505 wagon (and perhaps sedan) fuel sensors
can be affected by modern gasoline. They should not really even call that
stuff gasoline anymore. The non-leaded higher octane stuff has really
become a mixture of all kinds of hydrocarbons some pretty aromatic (poor
shelf life) and some that are plastic softeners. I've already done the
sensor in my 88 wagon at 130Kmiles. If you're swapping used sensors be
careful that you don't use one that may be already partially deformed.
-Jim