Downside to M3 setup in 330 4dr?

I recently swapped out 85k oem 330i suspension for 25k OEM M3 suspension. Everything fit fine and went in smoothly. Car ahdnles much better (also added turner sway bars)...

Yet, some folks in other threads maintain this is a bad idea that will not work out well...

Why not (other than argument, wasn't designed to...).

I'll tip my hand and say I have been told by BMW cert mechanic that it's totally fine/safe/effective approach..

Rear suspension should be the same since E46's are all about the same in the rear unless you have a vert or a touring.

Front spring rates and damping on the M3 will be slightly higher in the front relative to the rear because of the slightly heavier front end.

Handling wise, it will be sportier, but probably a bit more understeer near the limit, assuming all else like alignment and ride height, etc... are the same.

The sway bars on your 330 are not tuned specifically for the M3 suspension, which makes it a bit of a mismatch but I wouldn't think that will become problematic because many people change dampers and springs but keep the stock sway bars on their sled.

I'm pretty sure the angle of the front suspension in the M3 vs the non-M has it so you'll have less neg camber when running the OEM M3 in a non-M. That's about the only downside I would think there'd be, and you can always get some camberplates

Have you pushed the car to its limits yet? The stiffer front springs due to the M3's heavier cast iron engine block will increase understeer. You should at least be running a square setup to help neutralize the car a bit.

To the limits is relative no track days but have given it a good street thrashing and it feels great.

I'm on a square setup of 19x8/235/35.

Changing tire air pressures can induce understeer or oversteer, when you autocross/track play with those to dial it in to your liking

Interesting, what do you think ideal settings/psi would be to decrease under steer but remain safe/practical for street use?

I ask not because of the suspension update but because I'm always looking for less understeer, I think as a result of my years riding bikes.