The Front Sway Bar

The MR2s without a limited slip, tend to really spin the inside rear
tire coming out of corners. A huge factor in autocross is how fast one
can start powering out of the corner and get early on the acceleration
curve. The MR2, specially the NA MR2, is made for this with gobs of
torque and rear weight bias. But if the tire is spinning, you lose time.

The best solution is to go with a stiffer front Swaybar. Too stiff a bar
will mean the car will understeer. Too soft and the car spins the inside
rear tire. So what is the best solution? There isn't one.

Stock is X rotational stiffness, the TRD is 30% stiffer, the ST bar is
near 100% stiffer. ST designed the bar to be mated to a rear fatter bar,
but since we can not use a rear bar in SCCA stock, this is then too fat.
Note, some people like the stiffness of the full ST bar, and one way to
make it work, is by using softer bushings (stock Toyota ones that are
drilled out, or stock Neon bushings with 1/8" spacers under them). You
can also modify the ends of the bar to give yourself some adjustment.

It helps to understand what understeer and oversteer mean to your car at
different speeds, since this changes. A car that is neutral at a 50mph
sweeper, will tend to understeer in a 1st gear tight turn. But if you
set up the car for that 1st gear turn, it will probably be oversteering
at high speed manuevers. So, do you want to lose time in the slow stuff,
or in the fast stuff? My feeling is that you should bias the car to be
set up for higher speed turns and chicane/slaloms, and live with a
little push in very slow turns. You can compensate for this tight turn
push by driving technique.

I don't think the TRD bar is stiff enough. I have driven MR2s, including
93s with a TRD bar and I think there is too much rear wheel spin. One
other option is to beef up the TRD bar (be creative) or machine down the
ST bar. I think most of the work occurs along the straight axis of the
bar anyways, so focus your attention there.

Now, one downside of having a stiffer bar on the front, is that you
stress everything else attached to the bar, more than it was designed
for. Most common is the end links will bend, or the mounts to the end
links from the strut housing will separate. You can install 93 endlinks,
which will not bend, and you can beef up the welds on the attachment
points. There has also been a couple of cases of the mounts themsleves
ripping off the body, but I haven't seen this, and I am not sure how I
would fix it if it happened!