try this...

Center the trims on your radio. Put the servo horn on your servo as straight up as possible. Then use the SUB-TRIM on your radio to completely center the servo horn straight up. Adjust the servo horn to steering rack tierod so that the steering rack is centered while the servo horn is straight up. An easy way to do this is to use the the two screws that attach the graphite link to the steering rack arms (see photo). Now make sure you give your car zero degrees toe-in or toe-out with the steering tierods (at your preferred ride height with the equipment powered on). Then compare both steering tierods and make sure they are the same length as each other. Set the Dual Rate (D/R) on your radio to 125%. Now use the End Point Adjustment (EPA) on your radio (at your preferred ride height) and make sure the the steering blocks go all the way to full lock both left and right. That should be it, your car should turn in the same diameter circle on the track both left and right.

I use an Airtronics M11 and a Ko Propo Servo and my EPA is set to 80% both left and right with equal travel both ways. There might be slight differences using other equipment because servo travel is different between radios and servos.

Mark