Earlier this year, CARmag.co.za reported BMW had no plans to build a full-fat M performance version of the Z4 roadster, saying that the flagship M40i derivative, which we sampled in Portugal in 2018, is powerful enough. However, it seems that the folks over at G-Power disagree, as the German tuner has unveiled its replacement for a Z4 “M”.

The Brunsbüttel-based firm says it has made “extensive modifications” under the the third-generation Z4 M40i’s elongated hood. The 3,0-litre inline-six turbopetrol engine has received additional performance software, an uprated turbocharger (now with increased capacity) and an in-house-developed intercooler. Furthermore, revisions have been made to the exhaust system.

The B58 mill (which as standard churns out 225 kW and 500 N.m) now produces a whopping 368 kW and 700 N.m of torque. For reference, that’s 37 kW and 150 N.m more than the outgoing M4 Competition in coupé-guise. G-Power claims the Z4 M40i-based “M” is capable of achieving speeds “well over” 300 km/h.

The tuner says it anticipates that if the Bavarian automaker were to release a M derivative of its soft-top, the tuned version would “in all probability even outclass it”.

Exterior updates are subtle, with the tuner’s 20-inch Hurricane RR double-spoke alloys being the most notable additions. According to G-Power, the forged wheels have been designed for optimal weight reduction.