What is it?
BMW maintains there's no case for an M version of the Z4, so unless the demand for hot roadsters suddenly goes ballistic, the 35is, which we've now driven in the UK, is the fastest variant we'll get.
At 335bhp, the 35is has 33 more bhp than the regular 35i. There are some visual tweaks but chassis changes are limited.
What's it like?
Faster, certainly. Beyond a freer flowing exhaust there are no mechanical changes to the 35is's motor over the 35i's. That's okay – the turbocharged 3.0-litre 'six was already a stonker.
The way the 35is picks up and pulls cleanly through its rev range is world-class, and now it comes with the kind of exhaust rasp that's been missing from the line-up since the demise of the old M3. Economy and emissions are on a par with the regular 35i, too.
A seven-speed dual-clutch transmission is standard and, save for the usual second-first hesitancy when manoeuvring, it shifts cleanly.
It constitutes part of a generous standard kit-list that also includes lowered suspension with adaptive dampers and the option to choose between Normal, Sport and Sport+ settings.