I'm not much of a modder, but I recently learned about how much of a difference a rear engine mount (torque arm) can make for manual transmission drivers. And of course, I have a manual Fit (and also a manual Civic).

For the Civic, there are a lot of choices, but I settled on the PRL version.
But for the Fit, I didn't really see much. And to be honest, it has lost my Garage Princess status, so I didn't want to spend big bucks.
Enter PowerFlex PFF25-420. They have two different versions for CVT & manual. I guess it's really four different versions considering Street vs. Black Series).

Compared to even a stock Civic, Fit always felt loosy goosy, and hard to drive smoothly. Too much drivetrain slack.
I understand some of this is due to the clutch delay valve, but the whole engine & transmission wobbling around is a big problem, as I learned.

Short story short, it's great! Cheap. Easy to install. Hardly any added NVH. So much so, I'm flabbergasted how sloppy stock mount is, especially for the manual transmission models.

It's easier to drive smoothly, as it won't bounce around as much when you get it wrong. It also makes it easier to get it right, as everything feels a bit more taut and natural.

I imagine it won't make much, if any, difference for CVT drivers, but for manual drivers, I think it's a great simple mod.

Lastly, I got the regular yellow "Street" version. I'm kind of curious how much stiffer the "Black Series" is, but I'm not going to bother trying it out.
I'm perfectly happy with the "Street" version. It is my "regular car," after all.