18RSFive

Just wondering if anyone here has replaced the OEM sway bar bushings with poly bushings (2018 RS5). I don't want to replace the OEM sway bars as I don't want a harsher ride. Looking to possibly make the existing setup a tad "tighter". If you've done this, did you notice any added harshness or noise?

gk1

Any added perceived harshness would be from the hard bushing, not the bars themselves. The bars are twisted when they work so you would not notice any additional harshness with larger bars. However one could make the argument that any sudden jolts to the system would only transfer to the body as harshness via the poly bushings you would be looking to install.
Also IMO larger bars are a nice/noticeable difference (no harshness) and they include poly bushings. So I am doubtful there would be much noticeable difference with just poly bushings on stock bars. Plus it might be hard to get bushings that both fit the exact size of the bar (Audi is known to use fractional mm size bars and to fit the Audi OE brackets.) So you might have to fab alternate brackets.

BreedsAs

I have the 034 bars. No increased harshness was realized.

NJS5

Same on my S5 rear bar.

KevinGary

No harshness with my Eurocode bars

BreedsAs

The 034 bar is adjustable, so I'm sure you'll be fine with it's performance and rude quality.

RoB9

+3 No harshness with my aftermarket rear sway (034). I did think the rear SF mounts added a tad more vibration but it may be in my head.