I would say that #4 is the location of the intercooler for the turbo 2.2 Hamster edition motor.
Hey my first car had the ultimate old man sedan action going on. 1976 Chevy Chevelle 4 door complete with acres of chrome, powder blue paint, hubcaps (without the kung-fu grip) whitewalls and the mush-box luxury suspension and the smallest V-8 you get get in it the 2 barrel 305 making a whole 140 horsepower! (Later it went up to 200 with the same limp wristed carburetor after I did a head swap, I kept it on there to annoy my friends, which it did.)
Whenever I get my roll of film developed I'll post pictures of my 95.