I previously had an Acura TSX and upgrading the sway bars really improved the corner ability.

1. What are the plug and play upgrades for this model?

2. Which sway bar front or rear improves handling the most?

3. Which sway bar is easier (less labor)to swap and do?

Also, the 2006 RX 330 I believe is still on the original spark plugs. Should those be changed at the next oil change. No performance issue regarding it.

 

The rear sway bar can be done with the car on the ground in probably half an hour if you don't run into any rust. The front on the other hand is a massive ordeal and prob not worth it for a FWD as you'll just increase your understeer even more. More details about that in the other sway bar post I replied to.

There is an 18mm Cusco and a 19mm Ultra Racing bar rear bar for the FWD RX. The Cusco is a lot more easy on the wallet to buy and looks every bit as nice if not nicer than the UR bar. The rear bar will be your best bang for buck on these and really wakes up the car. Even the 18mm isn't really big enough in my opinion for these. The FWDs could probably get away with a 21 or 22 with the stock front 23mm bar. AWDs get very lift-off oversteery with 23mm and 22mm Addco 2109 rear bar (2001-2003 AWD Highlander or RX300 only), which is why my car has a 26mm front from a 2010-2015 RX350. That balanced it perfectly. Now there is a very predictable amount of lift-off oversteer without it being tail-happy

 

Is there a difference between the two options? Is the mm in thickness making any meaningful difference?

 

Never tried them so can't comment on them, but the Cusco is almost half the price so way more bang for buck for a reputable Japanese aftermarket part

4mm over the stock 14mm toothpick of a rear bar will make a noticeable difference