350 V6 (M272)
Kleemann offers a wide range of engine tuning products for the normally aspirated Mercedes-Benz M272 V6 engine. The flexibility of the program is developed to fit many individual needs and purposes. Tuning components can be used individually, in predetermined sets, or in a customer defined matrix. The available tuning components address all aspects of the engine and represent a “Stage” tuning concept ranging from K1 to K3.
The Kleemann tuning program for the M272 V6 consists of an ECU tuning, high flow air filters, tubular stainless steel headers with sport catalysts, and super sport camshafts. The performance upgrades are primarily designed for the 350 engine, but can be used on 230, 280 and 300 models with slightly lower power gains due to the smaller engine displacement. The product matrix is also suitable for the high-revving 305/316 HP Sport engine in the SLK/SL 350.
350 V6 (M272)
350-K1: ECU tuning. Up to 305 HP and 375 Nm (278 lb-ft) of torque.
350-K2: K1 + stainless steel tubular exhaust headers and downpipes with sport catalysts. Up to 320 HP and 390 Nm (289 lb-ft) of torque.
350-K3: K2 + super sport camshafts. Up to 340 HP and 400 Nm (296 lb-ft) of torque.
350 CGI V6 (M272)
350-K1(CGI): A custom made ECU software. Up to 335 HP and 425 Nm (319 lb-ft) of torque.
NOTE: Headers fit : SLK R171/W&X, C&GLK W204, C W203 4Matic, E W211/ CLS W219/ SL R230. LHD and RHD vehicles.[/quote]
I'm aware of these options, but I'm having trouble finding success (or failure) stories. The Kleeman website is even inconsistent -- on the page you quoted, they claim up to 305hp with just the ECU tune. On the product page for the ECU tune, they only claim a maximum of 290hp. That's a difference of a 22hp gain (probably not worth $1000+) vs a 37hp gain (a bit more worthwhile for $1000).
I've also seen a few threads from people who got the ECU tune and found they actually lost dyno hp. I haven't seen any threads from people who got the ECU tune and were totally blown away by the power it unlocked, which is a bit disconcerting. Same goes for the exhaust upgrade. Haven't seen any reviews on the camshaft upgrade.