Sway bars or Anti Roll bars.
As the name implies they hamper roll, equalizing both sides. We use them mainly to keep roll centers from migrating too much outside of the best working positions(they move when the car rolls). Now the thing that I found today looking at the cars I have with sway bars is that only two(Kyosho ZX5 and Mugen MBX5R) keep the rear bar mounting balls perpendicular to rear arms when the suspension works, all of them keep the front bar mounting balls almost perpendicular throughout suspension travel.
I'm going to think more about this, just found it a couple hours ago and want to know if this is supposed to happen, maybe not because the bar works by forces twisting itself, if the ball end is pushed back then the force the bar exerts towards the arm is somewhat lost, causing inconsistency in handling.

Later this evening, radio adjustments.

Part 2, radio adjustments.
Personally have 2 profiles, Mellow(or Main) and Aggressive(or Qualifying) to use in different situations in a race. They are a bit different to each other, I know most just change steering D/R or ATL but mine also have different expo values. So, during practice I test the fastest profile and make changes to both the car and radio until I'm satisfied with the speed and feel, that will be my Aggressive setup. Then I back out throttle EPA or add throttle exponential, use less D/R or steering exponential until I'm satisfied with consistency and pace and save that profile as Mellow.
That way my nerves don't get in the way the first laps and if I need more aggressiveness once I pit for fuel I change the profile. This is easy to do on the hacked GT3B, the M8 and CRX are not so easy, I use mainly ATL and D/R on those radios because those buttons are easy to reach.

P.S.:BTW I've driven lots of 1/8th buggies with Futaba S3003 and 4.8v Rx packs, for roughly half an hour they do OK on the track then the battery packs drops bellow usable voltage. It helps that my local track is wide(13ft lanes) and not tight at all, but at least newbies aren't in a rush to upgrade servos. The S3003 work not so bad with voltages upwards of 6v
Also my servo recommendation is:
for 1/8th buggy- ST/TB at least 8kg and .15s, personally anything above 12kg and below .1s is too expensive for the performance provided. If you feel otherwise maybe your car understeers