In my experience, I ran a K&N FIPK II on my 3.7L Liberty for about 35,000 miles. When I removed it, my mileage went up about 1.5MPG.

 

theoretically, this makes sense as the fuel a management system wants to balance the air/fuel ratio. More air, need more fuel. Considering the gains are negligible if any, there wouldn't be enough power to allow the engine to work easier, to which, if it did create that much more power it would conserve fuel.

 

I have an AFE cool air intake and throttle body spacer I didn't really notice anything. I wouldn't do it again waist of money in my opinion.

 

Yep hose are a total waste of money.

 

I've posted this link before and I'll post it again.
K&N Air Filter Review - Debunking the Myths (and why OEM is better)

I've run K&N and Holley shot filters in a cammed/head/long tubed 5.7 LS1 and running the stock air/ oiled air filter/ and a removed air filter on a dyno showed no HP gains on a DynoPro dyno what so ever! In fact the oiled filters are more work than they are worth. The time it takes to wash the air filter, let it dry, then oil it and then blow out the extra oil isn't worth my time in "Savings" of the $14 I spend at NAPA for a brand new Napa Gold air filter. I suppose the oiled filters are fine for you highway driving rigs, but anyone that has spent time in MOAB knows that the red dust can't be stopped by anything let alone an oiled filter with big ass holes in it. K&N filters are a scam.