XS3 is an excellent radio. You can use the steering servo for your throttle. But you have to install a very fast and strong digital servo with metal gears. Something on the lines of 0.9 speed and 120oz of torque.
Most people will tell you to try another motor than the Rossi Pixi. However, that is the engine I am using. It's a little picky day to day, but it runs like a champ if you know how to tune well. You can't run that engine how it comes in the box. You have to remove the shim and install a cold turbo plug to get any top end.
So, if you don't wanna deal with that, you should consider another engine.
Oh yeah, and Welcome to the G4 Elite Speedy1.