You have an 88 with the 302, right, bluesman17? Look on the side of the air filter box for a similar fitting. THe hose that fits from there to your cap-fitting is a vent for crankcase pressure. On higher-mileage engines, you will often get alot of oil on the filter thru this line. THis is also the thing that i told you about replacing with a simple breather cap with a built-in filter. You can then plug the fitting hole in the airbox, too.