To earn bonus parts, get an A or S on any mission.
Get CWG-ARF-180 Part
You must beat the game first to obtain this part. Go to zone 3 lab development, mission protect part transport. When the transport is refueling, destroy the rear cargo door and retreive the part.
Get KWEL-EJ22 Part
Zone 3 lab development, mission defend solar power plant. You must find this part. After you fend off the exterior attack, head inside. Then travel to the room that's on fire in the SOUTHWEST corner of the map. The part is on the floor in one of the corners.
Get KWI-RJ/60 Part
Zone 4 R&D Area, mission eliminate rioters. Proceed with the mission as normal, until you reach the top floor. When you get off the elevator, there will be 3 MT's and a crate right in front of you. Destroy the crate to receive the part.
Get MWC-OC/30 Part
Zone 7 unexplored region, secure unexplored region. When the mission starts, overboost forward until you fall into a crater. You will find a crashed transport. Destroy the rear door and retrieve the part.
Get Bonus Parts...