[belcom]

I've installed powerflex purple on the regular Z4 shortly after I got the car but at the same time I've also installed ST X coilovers. Before this the original suspension was completely shot and drove like crap. It was all over the place, harsh, unstable, just terrible. So these upgrades made a massive difference and steering is direct, responsive and sharp. It goes where you point it. I am sure poly fcabs contribute but its hard to say exactly how much though. I don't detect any additional NVH.

Z4M is in a whole different category as far as steering goes. It overall feels like a completely different car to begin with. Personally went with oem fcabs on this car. Its already very quick and sharp out of factory. Didn't think there's need to mess around here. No regrets.

OP, have you changed the RTABs yet? If not, I would highly recommend you do. OEM + RTAB limiters is good option. It will tighten up the rear. Alignment is required after that job.