LANZAROTE, Canary Islands - The SLK roadster - with its sleek lines, graphic interior and power-retractable hardtop tech- nological tour de force - was widely viewed as art on wheels when it bowed four years ago. But Mercedes executives believe the car truly is sitting pretty now.

The reason? A $75 million redo that includes the addition of an optional V-6 engine - the award winning (Ward's Ten Best three years running) 3.2L found in the CLK, E-Class and M-Class, plus a new 6-speed manual transmission for '01.

The V-6 provides more power and even more refinement to the 2-seater. And the new 6-speed, which debuted first on European E-Class sedans last year, helps move the roadster along the continuum from touring convertible to bona fide sports car.

More importantly, Mercedes believes it has hit the timing right. The upgrades help the SLK keep pace with the Porsche Boxster S that bowed last year. And with the Audi TT battling negative publicity over its alleged on-road instability and the BMW Z3 standing pat, the automaker thinks the door is open for the SLK to tighten its grip on market share leadership. The revamped model, launched in Europe in mid-March, hits the U.S. and Japan in April and bows in Brazil mid-year.

Even without a V-6, the roadster has performed well against the competition, Mercedes executives point out. The Bremen, Germany, assembly plant is building all the SLKs it can - roughly 50,000 annually - and there appears to be no let-up in sight for the current nine-month order backlog in Germany. Despite that, there are no plans to hike capacity, in part because the automaker is comfortable it has achieved an idyllic supply/demand balance.

The SLK takes a healthy 34% share of the luxury 2-seat roadster market in Western Europe, 37% in Germany, 12.6% in the U.S. and 47% in Brazil, Mercedes says.

The addition of the 3.2L V-6, which delivers 215-hp at 5,700 rpm and 229 lb.-ft. (310 Nm) of torque at 3,000 to 4,600 rpm, certainly adds a bit of muscle compared with the 190-hp (up 5 hp for '01) 2.3L supercharged 4-cyl. found in base SLKs in the U.S. But the V-6, which knocks 0.3 seconds off the 2.3L's 0-60 mph (97 km/h) times, is about refinement, not power.

Most of the benefit is in NVH (noise, vibration, harshness), where the smooth-running V-6's baritone exhaust plays symphony to the wheeze and whine of the more gritty supercharged engine, providing the SLK with an aural sensation of power the 4-banger can't match.

The new Mercedes-designed and-built 6-speed manual also proves a player in a midwinter top-down test-drive on an assortment of roads cutting through this remote tropical island's lava-littered landscape. Although not as crisp as some competitors - like the Honda S2000 and Audi TT - the new short-throw 6-speed is a welcome upgrade from the current car's rather pedestrian 5-speed manual. Also enhanced is the optional 5-speed automatic, which now can be shifted manually, as well.

Mercedes has big plans for the 6-speed manual, targeted for use in the upcoming C-Class to bow later this year. The first passenger car application for the manual/automatic - likely the CL coupe - is expected within two years.

The SLK's revamped exterior features new rocker panel cladding and front and rear aprons and turn signals integrated into the side mirrors. Inside, Mercedes ditches the carbon-fiber trim in favor of machined aluminum in the 4-cyl. and wood in the V-6.

Mercedes-Benz USA Inc. expects to sell about 12,750 SLKs in the U.S. this year, up from 10,600 in 1999. Pricing hasn't been set in the U.S. yet, but in Germany Mercedes is charging an 18% premium for the SLK 320.