Air filter/intake

Running a 2.2L, would I really notice any difference at all if I switched from the usual air filters to a K&N filter? to a K&N air intake system?

Very little.

not worth your time unless you are planing on keeping the truck more than a year longer, then by cleaning and not replacing it you will save money but other than that it would be pointless if you are looking for power

replacing the filter alone you will get a little better acceleration, remove the air silencer from the air box it's held in by rivets just drill them out or cut a large hole in the box, there is also a air chamber on the passenger side of the radiator a paint can cap clamps perfectly into the hole. the box clamped to the throttle body has a tube in it that can be removed for some better flow. all this may get you 10-15 hp all for just the price of a k&n filter, everything still looks stock an dyou get a much throatier intake sound