Bingo. Though mostly it was F350 and just a few F250 that were exempt from the 96 OBDII mandate. My 96 RCLB F350 has a 9100 GVWR and had all the smog equipment and exhaust manifold air injection. Had a C6 trans tooi believe it was 8800# GVWR. So the 96 F150/bronco would have the mass air 351 with no smog pump, but the F250+ (any truck above 8800#), would have the speed density 351, with that smog pump with the dual thermactor tubes.