But can you tell something about the delay? Do you see a big delay between touching the screen and the moovement of the vehicle?
My project has a VERY small delay at least 300 - 400 milliseconds, but that is caused by the time it takes to get the values from the accelerometer, process them and send them out. It looks almost instant, touch and responce.
The delay comes from what is inside your loop and what it has to process. My arduino is processing 3 accel axis', and the data from the touch screen; which is then sent out through the BT module.
I go with simple codes first, just so I know it works, then I make them more complex but also more efficient.