The 335is uses a specially tuned version of the N54 engine from the 335i, resulting in 320 horsepower and 332 lb-ft of torque, plus an overboost function raises torque to 370 lb-ft for up to 7 seconds.
The 335is uses a higher performance version of the N54 engine from the 2006-2009 335i, which increases boost from 8.7 to 11.6 PSI. This results in 320 horsepower and 332 lb-ft of torque, plus an overboost function raises torque to 370 lb-ft for up to 7 seconds.