Despite its current range-topping status, the G20 M340i xDrive failed to impress when we got behind the wheel. One thing it most certainly does have, however, is straight-line performance, but as is the way of the tuning world, G-Power felt it wasn’t enough.
Three levels of power are on offer, starting with the GP-420 kit and moving up to the GP-510. The baseline tune will cost you €1695 (approx. £1500), and is good for an F80 M3-rivalling 414bhp and 443lb ft of torque – the 0-62mph sprint drops four-tenths over factory to only 4.0sec, with top speed coming in at 186mph should you opt for the limiter removal.
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GP-470 requires a little more than an ECU tune, with a new stainless steel downpipe and less restrictive 200-cell catalytic converter allowing for reduced backpressure. The result is 464bhp and 479lb ft of torque, helping the 3-series sprint from standstill to 62mph in 3.8sec – cost for this upgrade starts from €4245 (approx. £3800).
Pushing the B58 straight-six to the max is G-Power’s GP-510 kit, adding a new turbocharger with enlarged compressor and turbine wheels and larger CNC-milled housings for higher peak boost. Combined with its sports downpipe, 200-cell catalytic converter and an ECU tune, output comes to a G20 M3-matching 503bhp and 509lb ft of torque, providing a 3.7sec 0-62mph time. It will set you back €5840 (approx. £5200), which doesn’t seem unreasonable when you consider the performance gains.
All three stages offer improved throttle response, torque delivery and, supposedly, fuel economy (though that will be entirely dependent on a well-trained right foot…). A valved exhaust system with larger exits, the 186mph top speed increase, aluminium intake pipes, lightweight 20-inch forged wheels and much more are available across all three variants.