This weekend I read the air filtration study that Spicer had a company conduct on the various air filters. Good reading and great job Spicer. :ro) Most of you have likely already read it, I saw the thread several months back in its infancy and hadn't read the final conclusions.

While those with AFE Pro Guard 7's, AFE Stage 2's, K&N's, Unifoam's, etc. may take exception with the study, it turns out the AC Delco air filters are very effective at filtering and flowing air with little degradation of air flow, even for racing. :rolleyes:

Several months back I purchased a Unifoam air filter. I put about 8k miles on the truck with this filter. Yesterday I decided to pull the Uni and put my original OEM filter back in. The Unifoam filter was filthy, which on the face of it should be good news since that crap, as least the big stuff, didn't make it into the LLY. What I didn't expect was the "sludge" looking film over half of the filter, apparently where the majority of air moved across/through the filter. I could tell the air flow had been trying to get around this area since the sides of the filter were clogged as well on the filthy side but clean on the other side of the airbox. I saw no indication the dirty air was getting around the gasket and into the intake. Interesting! :(

I expected to see a lot of dirt and particles after 8k miles. My question is where did that sludge looking stuuff come from? :confused: The intake side of the filter was pretty clean. I can only imagine the air restriction the filter was causing my LLY. On the other hand my mpg's and EGT's should be better! JJ :)