How to replace the air filter on a 1991 V6 Toyota truck?

I recently bought a used 1991 V6 Toyota truck. It was one of the trucks that Toyota did a recall on, so it has a rebuilt engine. My problem is that I can find the air filter case, but I can't open it for the life of me! I looked all around it and there are no clips or anything...I tried just pulling on it, I tried wedging a screwdriver underneath the lid...nothing works! Before I bought the truck, it had been sitting for about 2 years. I don't know if that has anything to do with anything but I thought I'd throw that info in haha. I'd appreciate any solutions anyone might have!