I have a early 044 and a 660 the 44 has a blue foam insert inside the air filter and the 660 has a plastic insert that fits inside the filter with slots in it ....I have always assumed that they are a intake noise reduction feature the the foam inside the 44 filter makes me think I should take it out for a power gain of some kind...what says you? They both run nice and although not modded except for a duel port muffler and tune have plenty of power....also have a good holiday!