if you have too may unfermentable long chain sugars, beano(alpha amalyse) can break the long chains into fermentable sugars that the yeast can use.
i used it once when my barley wine stalled and it got it down a few more points.
warning - if used, fermentation can go a lot longer than you may be prepared for.
(almost had a batch of bottle bombs - have vented the bottles 4 or 5 times since april /06)
beer, wine, cheese in various stages of production