Check Torques for the Bonus Package grenade mod

Research and Development, in the area where Torques and Badass Torques appear.

Before you go

Reach Research and Development.
Bring weapons suited to the enemies in the area and enough ammunition for the route.
Keep inventory room for grenade mods and other potential upgrades.

Enter Research and Development and follow the route toward the Torque encounters.
Engage Torques and Badass Torques as they appear.
Defeat each enemy and examine the drops for the Bonus Package grenade mod.
Compare any grenade mod with your current setup before replacing it.
Loot nearby red chests and lockers as you continue through the map.
After completing the route, leave the map and save and quit to reset it.
Reload and repeat the Torque checks if the target is still useful to your build.

Inspect drops after both enemy fights; the target is associated with the Torques encounters, but is not guaranteed.
Use the full route when you also want general loot, then prioritize the target enemies on later visits.

Repeatable after resetting the map. The Bonus Package is a chance drop, and each route can also yield other gear.

Treating the Bonus Package as guaranteed can make the farm feel misleading; judge progress by actual drops.
Skipping the second named encounter reduces your chances to check the route; clear both Torques and Badass Torques.
Replacing a working grenade mod without comparing effects can hurt your build; inspect item stats and behavior.

Stop when you find a Bonus Package that works for your character or when your grenade slot is already adequately equipped.

Sources & fact checks

Open a guide to find other locations and see what the item is used for.

Legendary gear and Grinder outputs

Torques and Badass Torques offer a chance at the Bonus Package during the Research and Development clear.