High frequency suppression causes this drive to appear red under boost.
Permanently upgrades an equipped Rare Sparrow to improve speed and durability.
― In-game description

A Stealth Drive increases both speed and durability of a Guardian's equipped rare Sparrow and turns the boost contrail red. The upgrade is a one-use consumable item that transforms the equipped rare Sparrow into a legendary Sparrow. It can be purchased from Xûr.