Ron,
If you don't use Chevron or Texaco gasoline, and especially if you ever use raw gasoline without any additives like Costco or grocery stores sell, I would add Techron to my tank once a month. The cheapest place to buy it is at any Chevron Station or in an auto parts store in areas that don't sell Chevron gas. Porsche parts departments also sell Techron re-badged as Porsche fuel additive for about 4X the price but it is just regular Techron and is labeled as such on the back of the bottle. Nothing works better to keep carbon and other deposits off of intake and exhaust valves.
Chip