We recommend the 55W ballasts to those who really want to squeeze out every possible lumen of light. These replacement headlight ballasts are approximately 30% brighter than the 35W ballasts.
However, they are larger in size and run hotter. This additional heat can potentially cause premature wear to the bulbs and projector bowls. It also has a higher tendency to cause some fogging inside the lens. The additional heat generated from the ballasts needs to normalize with the temperatures inside and outside of the headlight.
You may see some fogging with these but it typically clears up shortly after the headlights are turned off.
These replacement headlight ballasts are recommended for the ''extreme'' retrofitter.