I've made some observations on my new car after some months of breaking it in. I have the 2014 2.0L skyactiv with the 6spd manual transmission...

I feel like with the VVT valve timing, the car should be able to drive pretty aggressively when you want to. But there seems to be a few aspects of the car that are limiting 'spirited' driving. The engine clearly needs to 'breath' better, but I know how to handle that. My questions are about the other two issues I'm having:

First, I notice that when I rev the engine to high rpm (say by reving it to 5500rpm before shifting to the next gear)... it seems like the synchros in the transmission are abysmally bad at allowing a fast shift. It shifts very smooth and great at lower rpm driving. But when rev'd high in the previous gear, the shifter wants to bounce off the next gear when you shift. It just feels like the synchros aren't getting the job done. I've had to learn to shift a little slower and more deliberately, and use a bit more arm force, when running the engine to high rpm.

- Question: Has anyone else noticed this? Does it go away with more breaking in (8.5k mileage currently)? Is it just a matter of learning to shift more slowly? Or does my particular car have especially bad synchros? Bushings? Linkage? Thoughts?

Second, the car likes to break traction on the front right tire when accelerating into a right hand turn. I know the cause, this happens whenever you have no limited slip differential up front, and the rear suspension is a little less 'tight' than the front suspension. The car will lean into that rear driver side wheel, and the opposite corner (where all of the engine power is going) has poor grip. The weight of the car also tends to lurch rearward some whenever you accelerate sharply. I think the rear springs are just a little too soft. The front seems great, handles well, tames bumps well, doesn't dip into hard braking. But the rear is a bit softer, and it degrades the car's balance.

- Question: does anyone know a specific replacement rear spring part, mazda or aftermarket, that would stiffen up the rear without raising or lowering it noticeably? I know I can put a stiff tubular rear sway bar on to help with the turning traction up front, but I think stiffer rear springs would help the car's overall poise more. But I do not want to lower the car. (actually, secondary question, is there a limited slip differential available for a 2.0L skyactiv manual?)