3 Commando Brigade

Ace 3 sucks the life out of my cpu.

You aren't alone in this. During testing of the Javelin that is being added to the weapon pack, we noticed FPS drops when using the launcher with ACE3. Fearing it was something we had done, we tried it with the vanilla Titan and you get the same issue. FPS drops. You can replicate it by doing the following and actually watch your FPS tick down 1 frame at a time.

Test:  
Mods: Only ACE
Mission in VR with single vehicle and VA
Select backpack and titan
Fire at vehicle
Lower Titan, but do not swap weapon

Frame rate slowly drops to 1fps

Drop titan
Pick back up
Frame rate back to normal.

Swapping weapons also restores fps