About 30 minutes later, we're heading onto the streets surrounding the New Jersey Motorsports Park in an sDrive35is, one of two models the automaker produces with this "overboost" function (the other being the 2011 335is Coupe). The yee-haw! feature is reserved for only the latest sport rides wearing the famed "is" badge. Our car burbles at idle, warmed up, prepped, and ready for action. It's time to see what it's all about...

To those uninitiated in BMW's model parlance, "is" is the brand's performance level set between regular models and those specifically tinkered by M GmbH, the creator of the brand's most powerful speed hungry machines. The line was birthed in the 1980s when the E21 320is hit world markets and ever since, has served as a happy medium for buyers wanting a tad more speed for a smaller price premium.

Although it would be convenient for BMW to simply call the sDrive35is a "Z4 M," it's definitely no M. Here's why: First, its exterior form is nearly a spitting image M Sport Package-equipped Z4s. Second, it's no lighter than the common model on which it's based and utilizes the standard model's brakes and suspension, among other crucial get-quick parts. Lastly, the powertrain, though more powerful, hasn't been fine tuned and bolstered using sturdier M division components.

Whereas M's creations yell, "Look, I can go fast," with their bulbous haunches, bigger wheels, massive binders, and motorsport stances, the 35is wears an M Sport Aerodynamic kit as standard (optional on all Z4s), uniquely designed 18-inch rollers (19-inch optional), and subtle touches like blacked-out exhaust tips with bolder surrounds, silver mirror encasings, and a matte aluminum bar in the lower front intake grille. Speed in an "is" is coyly understated.

Each sDrive35is packs an easier-breathing, direct-injected 3.0-liter straight-six paired with twin turbochargers churning at an increased boost pressure of 11.6 psi versus the usual 8.7 psi. Total output now stands at 335 horsepower at 5900 rpm and 332 pound-feet at 1500 rpm. It's 35 horses more powerful and offers 32 more pound-feet of pulling grunt than the tamer sDrive35i, its next closest sibling.

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Compared to the 35i's N54 series engine, the sDrive35is' engine achieves max power and torque 100 rpm later. It's a hellion of a powerplant bent on hitting law-breaking speeds as hastily as it can.

Despite the power increase, the 35is is no thirstier for premium fuel than the regular 35i with DCT (17 mpg city/ 24 mpg highway), nor is it heftier at 3549 pounds. It's somewhat green too, utilizing a mild regenerative braking system (think of it as a civilized F1-derived KERS) to power auxiliary components on-demand.

The whole is only mated to the brand's tried and tested seven-speed dual-clutch transmission (DCT) providing millisecond shifts at the push/pull of awkward-looking wheel-mounted plastic toggles, or by way of the standard gearshift. Shifts are quickened for the 35is with a lighter weight dual-mass flywheel and revised DCT programming.

The major fault of the 'box's setup are the paddle shifters. Make no mistake, they're no true positive upshift, negative downshift paddles. They're confusing as hell, not to mention unnatural, cheap in hand, and look as if they've been pulled off an early 1990s Big Foot Power Wheels. Cool aluminum upshift/downshift paddles like those on all other DCT-equipped vehicles aren't available on the 35is. According to BMW, they're on their way.

Turning right onto flat straight line road known as County Route 555, we remember the last time we had a Z4 in our garage. It was a few months ago during our roadster comparo when it was joined by three of its closest competitors. We tirelessly flogged a six-speed manual sDrive35i on L.A. County's quick-switching, off-cambered, decreasing radius roads.

The sDrive35i ended up placing third -- nearly fourth -- in the comparison, behind a second place Audi TTS and winner Boxster S. We were shockingly disappointed with the sDrive35i's un-BMW-like chassis imbalance, harsh suspension, and it's awkwardly matched engine/transmission setup.