I have the dx3 with a B4 I have to set the ST.TRIM to 21 and SB TRIM TO 30 to get the wheels straight does this seem ok? With both set to zero wheels are hard right! Cheers

I do not have a DX3 but I the first thing I would check is if you install the steering linkage when the servo is at neutral position with all trims set at zero.

the servo will sit up straight when you turn on the transmitter it kicks to the left bout 45 degrees.

Take the servo horn off of the servo. (it should pull straight off after removing the center screw)
Turn both trims on the radio to 0.
Turn the car on.
Then start to reinstall the servo horn on the splined servo shaft with the wheels as close to straight as possible.
Turn the car off and screw the servo horn on fully. (don't want to fight the servo while on)
Then turn back on and use sub trim to center the steering. (drive car a little to help check)
Then set the end points (EPA) for left/right travel. (close to full travel without any binding, have steering dual rate at 100)
This will get you close, then fine tune trim as needed to get it straight while driving.

Spot on thanks for that!