You can adjust the effectiveness of the rudder using
rudder_effectiveness=1.0 under the [flight_tuning] entry in the aircraft.cfg file. Max setting is 2.0 and min is 0.1
I sort this setting out before I adjust the slopes in FSUIPC.
The other setting you can adjust is found under [contact_points]
point.0=1, 2.4, 0, -3.9, 1181, 0, 0.523, 40, 0.15, 2.5, 0.808, 3, 3, 0, 176, 220
This is the nose wheel setting and the 40 in bold is the angle in degrees that the wheel can pivot left or right this also can be adjusted to suit taxiing effectiveness. However, this will also affect the aircraft turning radius. Change this as last resort. I have seen some aircraft as high as 75.