[markwilliamson2001]

Sounds like to me a number of things:

1) You don't have the stiff servo saver spring in
2) You don't have enough steering lock
3) Your front shocks are leant over too much

Check the first two, steering lock can cause massive sensation of understeer. I reduce mine on very high grip carpet indoor tracks slightly. It just takes the edge of the steering and stops it being twitchy.

I would run the front shocks: middle on tower, and inner on front arms. This should give you much more steering. Also run the front link on the inside holes on both the car and front caster block.