Top Speed has already shown you the German tuner Hamann’s take on BMW’s redesigned roadster, the Z4. There is another group of tuners in the Bavarian region that are out to make the drop top Bimmer even more of a sporty ride.
The tuning house G-Power starts off by adding a set of their signature Silverstone wheels and height-adjustable G-POWER coil-overs in order to achieve the perfect stance. The GZ4-RS, 9 way adjustable shock absorbers also help to tune the dampening characteristics of the Z4 to work best with the sticky 295 series rubber incase there is a challenge regarding the vehicle’s handling abilities.
The German mechanics have managed to keep the grease out from under their fingernails. Tahnks to factory plug and play connectors, they have been able to extract an additional 45 HP from the car’s twin turbo straight six 100% electronically, increasing the output of G-Power’s Z4 sDrive 35i to 345 HP, good enough to get the new BMW to sprint from 0 to 60 PH in just 4.7 seconds down from the standard version’s 5.1 second 0 to 60 MPH time.
Press release after the jump.
Press release
G-POWER isn’t just fast when it comes to HIGH-SPEED world records.
The all new BMW Z4 is hot when it comes from the factory. Now G-POWER makes it even hotter.
The G-POWER BI-TRONIK performance module pushes the factory 306 hp/400 Nm to 345 hp/480 Nm. 20 inch G-POWER “SILVERSTONE DIAMOND” alloy wheels with MICHELIN Pilot Sport tyres in the dimension 255/30 ZR 20 and 295/25 ZR 20, G-POWER coil-over suspension and a stainless steel sport rear muffler featuring the legendary G-POWER “DEEPTONE” technology round up the G-POWER package for the BMW Z4 E89. 
The G-POWER program for the BMW Z4 E89 touches all key components and lets the nifty BMW Z4 appear even more sporty, beautiful and last but not least exclusive. At first one will notice the especially for the current BMW models designed 20 inch G-POWER SILVERSTONE alloy wheels. Due to the successful combination of double spokes and the "concave design" typical of G-POWER they highlight the breathtaking design of the new BMW Z4 and so separate it for the rest of the mass production. The G-POWER “diamond cut” provides for the fascinating dynamic appearance of the G-POWER SILVESTONE rim, in contrast to the silver-graphite coated rim body and the bolt applications of stainless steel. An additional feature of the G-POWER SILVERSTONE rim is its weight-optimised design that allows a low rim weight with the same stability, compared to other standard wheels. A perceptibly improved impression of convenience and a considerably increased agility accompany the minimisation of the unsprung mass: advantages of the G-POWER SILVERSTONE rim, which you can factually experience especially in combination with the low-profile tyres from MICHELIN in the dimension 255/30 ZR 20 and 295/25 ZR 20. Further improvement of the road handling is realized through the continuously height-adjustable G-POWER coil-over suspension GZ4-RS with nine selectable settings each for bound and rebound. 
In order to benefit from the improvements of road handling and cornering realised by the G-POWER products, the factory output even in the strongest version provided by BMW, the Z4 sDrive 35i, is not enough. That is why G-POWER offers the performance module BI-TRONIK that pushes the factory performance from a standard 306 hp/400 Nm to a more satisfying 345 hp and even more important 480 Nm of torque. In doing so, as for all performance increasing projects of G-POWER, reliability and durability were the top priorities during the development of the BI-TRONIK. Nevertheless, a performance and a torque increase of approx. 20% could be realised. Due to the use of original plug-in connectors, the G-POWER BI-TRONIK can be easily and quickly integrated; residue-free removal is possible, as well. Of course, all standard engine protection and diagnostic functions of the engine control unit are maintained to full extent.
Naturally the performance figures benefit from this output improvement. The figure from stand still to 100 km/h is now less than 5 seconds (4,7 seconds). 
Next to the output and the suspension of the BMW Z4, G-POWER has taken care of the sound, as well. The full stainless steal G-POWER 4-trim sport rear muffler with its 4 x 83 mm tailpipes gives the BMW Z4 a deep, throaty sound that turns heads but is at now time annoying, thanks to the patented G-POWER “DEEPTONE” technology.