BMW‘s North American division has set its eyes on the lucrative aftermarket business with the releases of two performance packages for the 135i Coupe and 335i models.

The stage 1 and 2 Power Kits for the aforementioned models are fully covered under BMW of North America’s limited warranty and can be retrofitted at BMW centers or via the Port Installation Program.

The version 1 Power Kit, which is also available for X6 crossovers produced up to April of 2010, includes an engine software optimization that increases output by 20HP to 320-horses, and peak torque from 300 lb-ft to 332 lb-ft when equipped with an automatic transmission, and 317 lb-ft when fitted with a manual or DCT transmission.

According to BMW, with this kit, the 335i completes the 0-60mph (96km/h) sprint 0.2 seconds faster than the standard model. It is also 0.5 seconds faster in the 50mph to 75mph acceleration and offers what the company describes as an ““Exhaust burble” sound during engine overrun conditions.

The version 2 Power Kit includes the ECU upgrade plus an auxiliary water cooler and an enhanced radiator fan to reduce the higher thermal stresses on the engine during extreme driving, according to the automaker. It is available only on the 135i and 335i.

BMW said it is offering a special introductory price on all Power Kits from now until the end of 2011, with the Version 1 Power Kit carrying an MSRP of $599, and the Version 2 Power Kit an MSRP of $1,199. Installation costs are not included in the above prices.

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