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you say the gen4 Camry platform has a front sway bar, do the gen4 es300 platform have front sway bars also?
Yes, you basically have a gen 4 Camry, just with better parts, build quality, looks nicer, far better interior/body etc. And it's built in japan only

I.E. Toyota Windom woo woot!
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(i dont know how your suspension is setup) but why did you consider getting a Whiteline rear sway bar? do you feel any improvements having it?
(correct me if i am wrong) is the purpose of a rear sway bar to control the rear end as you manuever through a turn?
Without going into how the physics work out. The stronger the bar, the less grip that end of the car has. (Hence, the more lateral traction the opposite end of the car has). and vice-versa.
Because in almost every FWD car, you are understeering (loosing traction on the front wheels when applying poewr during cornering, or just all the time for almost all factory cars.), you want MORE front traction.
A larger rear sway bar will let the back end slide more, while giving the front end more traction. Which is exactly what you want.
In the process the body roll is much, much less, while the steering, and tracking usually sharpen somewhat.
In the case of the 97-01's, because the front bar is still somewhat too small, you can upgrade those as well to help balance the car.
Most manufactureres set cars up to understeer. Loose grip in the front wheels. It's the bad way to go around a corner fast, but if you do loose it, atleast the nose of the car will continue to go in the same direction. (better for newbs) With most rear sway bar upgrades on a FWD car. You will still understeer around most corners hustling, but you can induce oversteer (the back end sliding out, or wanting to spin out) easily enough. A quick flip the the wheel & mild counter-steer, or a flip of the wheel & a shot of gas pedal is all it takes. In any event, instead of just sliding out of a corner, a RSB will take out some body roll, and help neutralize the handling.
Without doing an major money / suspension changes. A rear sway bar is *the* first thing to upgrade on any FWD car. It's the biggest change for the money, makes a big change period, and even if you have the money for big mods, it's very high on the mod list of "I have to have that period".