Just purchased a replacement K&N Air Filter (p/n 33-2298) for my '05 4.0. Never used one of these on any car I've had before but obviously heard lots of good things for many years. I'd like to get some opinions from those of you who have used them in your new 4.0s as to what to expect from it...in the real world. Gas mileage, acceleration, etc. Does it make much of a difference in any category with a bone-stock 5-speed Mustang V6 or am I buying a never-needs-to-be-replaced air filter with no additional benefits? I'm not looking for "you should've bought a GT" or "go with the cold-air intake" answers. I'd like to take this one small step at a time with a car I truly can't get enough of. Thanks in advance!