If your airbox is cut up, get a K&N Intake Kit. If not, get a drop in K&N. I can tell you from experience the stock paper filters are more restrictive than a K&N filter. As far as CAIs being a rip off, I have road and dyno experience to call BS on the claims they do nothing. Will you gain 10-15hp as they claim? Will you gain mpg? Depends on other variables such as how restrictive your intake is and other mods. Example:
02 ZX2 I had the intake was very restrictive, modded the airbox and added a K&N gained 4mpg on avg
02 Mustang GT I have baseline 231rwhp 279 lbs/ft: CAI (fenderwell), catback, larger TB, UDP, tune= 254rwhp and 314lbs/ft the intake alone was worth 3rwhp (dynoed) tuning and a larger tb & plenum helped alot, mpg I cannot say because I did a gear swap and lost 6mpg on avg.
I do not think the 4.0SOHC Ranger has a very restrictive intake so, I would only change the filter to a K&N. You will probably only see 1mpg maybe 2 due to gearing of these trucks. Add a Catback to free up more restriction. That should give you maybe 3-4mpg at most and I am being generous. A light foot helps but, not much. These trucks are not geared for gas mileage. The K&N will pay for itself as you only have to clean and never change it. So $45 once or $15 every couple thousand miles? Want a better gas mileage than that, run a lower gear set, that is where you will notice a larger gain. Go 3.55s or 3.23s.
Last edited by Sad Ranger; 02-02-2012 at 08:06 AM.