How old is the filter? Is the tank metal? I've heard that filters can plug real quick when converting to e85 especially with a metal tank. My tank is plastic and I changed the filter a week or so after my convert and tune and it was totally clean. In my case it was good to be safe rather than sorry. If your filter is old and your tank is metal I'd change that filer asap. e85 will clean a metal tank really quick and the particles will get plugged in your filter.