I'm looking to lower my 14 IS350 f-sport RWD. Has anyone tried the factory F-sports lowering springs? How low it can go? Or some other brands u guys recommend?
One thing I'm not sure is whether the lowering springs will work well with the adjustable suspension on the car？ Since it will tighten the suspension for Sports+ Mode.

 

Take a look at the suspension section, there's at least over 20 posts that are helpful in some ways. Just browse through it and all your answers will be there

 

Springs will still work with the Sports+ AVS feature

 

How many miles on your car?

f it has 40k miles ish, you're better off just getting a set of coilovers, especially being in the snow belt, the nut shock/damper shafts might seize or get stripped if you are putting in springs. From experience here. My '14 was stock when I got it, I was planning on springs, but with 40K on it, I figured the factory suspension was pretty close to being worn out, considering all the potholes around and the two bent oem wheels I ended up having when they got refinished.

Loosing the AVS feature is no big deal IMO. You still get the improved throttle response and stiffened up steering, but dampening you want all all times.