On my 1990 it had the squareish box thats in your pic, the one in the left upper hand corner. The elbow I replaced it with came off a 1989 removeable top 4-runner. That is show in the pic Mike took for me. Your 88 runner would have came stock with this elbow. My truck came stock with the SDB.
This made a difference for the elbow is straight throught while the SDB has this port in the center of the arch. I beleave the port to cause more turbulance which slowed the air down.
