2.2 and 2.5L are in the same location. In the rear of the valve cover. You'll see a hose coming off the cover, its just in back of the oil filler cap, in the hose the PCV valve sits.
On a 2.6L engine it screws into the valve cover and blends in with it. It has a 5/16ths inch hose comuing off it and a 14mm wrench is used to loosen it because its a Mitsubishi engine(2.6). It is rare to find a 2.6 in an 88 K-car.