Have you guys come up with a solution for the horrible understeer these cars have?

AC

 

Sure, get an alignment with camber bolts for at least -1.5 of camber. Get higher performance lower tread wear tires.

You can go into additional suspension work after that.... The added on progress rear "sway bar" is a great choice.

 

Make your rear tire pressure higher than the front, I run 3 lbs higher in the rear.. But mine is a GD sport with a rear factory sway bar. I have a Hatchback RWD BMW that requires this out of the box, factory front tire pressure is 28 rear is 34. If you don't run the split the bugger is a scary B**ch to drive. Just set your pressure on cold tires and add a lb and test until you find the sweet spot. Usually its 6 lbs or less. (Tires matter... too...)

 

Or get a bigger anti roll bar $200 max or 10mm spacers $50 max. That's what I'll start doing before rear sway bar.

 

If you are adjustable there is useful info on this in the gd suspension section in the sticky thread "suspension theory".

 

Stiffening the front without the back usually results in more under-steer.
Tire pressure is free and it will make a difference.. although smaller than a sway bar..

FWIW my 07 really doesn't under-steer till your passing the limit.. But then its a little late.. And I'm running pretty thin tires right now..

 

Agree with this. You'd be surprised how much tire pressure can help before any other mods.

What scenario are you experiencing understeer though? An auto-x setup vs. track setup vs. a street setup is going to be very different. Do you have any current suspension modifications? What are your current tires?