BMW 335i Convertible Receives a Power-Boost from ATT TEC

German tuning shop ATT TEC is trying to further close the performance gap between the BMW 335i and M3 Convertibles with the release of a new sport package that includes two stages of power upgrades. ATT TEC's basic kit, which is priced at €2,355, takes the 335i's standard 3.0-liter twin-turbocharged straight six from 306 HP and 400 Nm of torque to 345 HP and 481 Nm. For €4,130, ATT TEC will