With its 4.4-liter V8 that produces 523 hp and 553 lb-ft of torque, the M850i is the most powerful member of the new BMW 8 Series family. This will soon change, however, as the full-fat BMW M8 is slated to arrive later this year for the first time in the model's history. While that will increase output to over 600 hp, a range-topping M8 Competition could even have as much as 630 hp on tap.

If, however, you can't wait for the M8 to arrive, there are plenty of aftermarket alternatives. The latest comes from German tuner G-Power, which recently turned the BMW M6 Coupe into an 800-hp supercar, and has specialized in performance optimizations on BMW models for more than 35 years

Impressively, the tuner's upgrade kit increases the 8 Series' output to a respectable 670 horsepower and 656 lb-ft of torque - that's a 147-hp increase over the standard model. As a result of this upgrade, the modified BMW M850i will now sprint to 0-62 mph in just 3.1 seconds and hit a top speed of around 199 mph. By comparison, the stock M850i needs 3.7 seconds to do the same sprint and has a limited top speed of 155 mph.

Several hardware and software modifications were made to improve the M850i's performance. G-Power has installed a set of stainless-steel downpipes including 200-cell sports catalytic converters that reduce both the thermal load and the dynamic pressure, allowing the twin-charged V8 engine to breathe more easily. This will set you back an additional 4,155 euros ($4,742), while the tuner's V2 Performance Software that increases the output costs an extra 2,481 euros ($2,831).

If you want to increase the top speed, this will cost you an extra 500 euros ($570). G-Power also adds a set of 21-inch forged rims with five classic double spokes wrapped in high-performance 255/30R21 and 305/25R21 tires, which are available for an extra 7,521 euros ($8,577).