A drop in filter will not do much if any in terms of performance/milage. The stock intake is still there. It still uses the somewhat restrictive stock intake.
Granted, the name cold air filter is a little misleading. From what I've heard regarding intakes for the F150, the stock intake is the "coldest" as far as intake temperature, mostly since it draws the air from the side fender. I've watched the IAT with my AFE intake, and the temp will climb in the summer when you are idling in traffic, but it will come down to a few degrees above ambient once you start moving.
As far as MAF fouling, it is possible to do so with any of the oiled intakes. If you over oil (after you clean it) the filter, excess oil will get sucked into the intake, and coat the MAF wire, burning it out. At that point, it technically is your fault. Granted, this shouldn't have happened if hadn't yet oiled it since you bought it (since they oil them pretty well at the factory.)
As far as tuning, the way the do it, IIRC, is they just lean out the mixture to get you more power (and use less fuel?). Well, that, and adjust shift points and what not.
Could be wrong on some of the above, though.
