Few Simple Questions

Have you centered the servo? It's easy to do and only takes about 30 seconds. Also, even the stock radios will have a steering trim. Remove the servo saver or horn, turn your radio on and set the steering trim to dead center or zero. Turn on the receiver in the truck, the servo will turn just a bit when turn it on and when it stops, put the saver or horn back on as close to having the wheels straight as you can. Then you can fine tune it from there when you run with the trim on the radio.