A filter wrap does increase the restriction by about 3-5% versus a clean filter without a wrap; however, you will more than make this up under real world conditions, as the filter wrap will improve the airflow over the life of the filter by keeping out the larger particles, bugs etc. The filter wrap does need to be cleaned periodically as it accumulates dirt by simply rinsing it out with warm water and dish soap.

 

If you are using a cleanable filter, the filter wrap will make the filter much easier to maintain as well, and the cleaner the filter is the better it will flow.