you might want to look into a hh or a heading hold gyro, that should help keep your wheels straight for sure. I know the 401 is a really good heli gyro for about $140, but I have no idea what you would need to race in a car. They weigh about 29g or so, but that's probably not nearly as important in a car

The gryo's from cheapest to most expensive run about like this

esky HH $40 or so
telebee HH $50 to $60
align $80
g90 $90
lt2100 $90 to $100
gy240 $120ish
gy401 $140ish

The order in heli's as far as performance is probably something like this gy401, lt2100, gy240/g90, align/telebee, then esky

All these models are HH, and some have remote gain, I dunno of what use that would be to you, but I know the gy401, lt2100, g90, and telebee all have remote gyro gain

The only one that I know that doesn't have it is the gy240

hopefully that helps a bit