After destroying the Harrier between the two shells. Simply run up the ramp caused by the crash. As you approach the edge do a Cartwheel and with any luck you should land on the ledge which had been cut off. Put the fire out with the coolant spray to reveal the case containing the suppressor.
I know for certain can be found here on difficulty levels V. easy, easy and Normal.
Codec Stuff
The left and right analog sticks will rotate faces, while depressing them will zoom. R1 or R2 allow you to overhear their thoughts.
Stronger Grip
100 pull-ups will raise the grip meter.
Birthday Surprise
Match your birthday to the date on your PS2 in the Plant episode to receive a birthday message.