I checked my pcv line too and the entrance between the rubber connector and pcv air line, it's a bit wet, is this supposed to be?

 

To the original question:

No, the cabin filter doesn't have anything to do with engine performance. It usually lasts for years before changing it. If you drive through dirty/dusty areas on a regular basis, like construction areas, you'll want to check it and change it more often. But it's not the easiest thing to get to.

It's under the plastic cowling under the passenger side windshield wiper. And if you don't re-assemble it properly, you can cause water leakage into your passenger side footwell. There's an instructional How-To guide in the forum's How-To section.

 

Note to my knowledge. Can you tell what it is wet with? Oil?

 

Not sure, feels kinda like oil, but some type of lubericant from what I can tell...I just never noticed it before. It doesnt really give off the smell of motor oil. However I have seemed to have fixed the problem significantly. I pulled off my MAF and rubber tube connecting to my Throttle, and sprayed With MAF cleaner. Now im avging maybe 18-20 street, and 28-29 highway easy. At one point of time with cruse control, and resetting the meter, my gas mpg went up as high as 31, and stayed at 29-31 for atleast a hour until traffic slowed down. This was all at 70-80 mph. And in a v8 O_O. Now street wise the meter says 22-23.

 

A little oil in there can make sense given where PCV is and what it does.

Glad that is yielding some improvement!!