You would probably want to scale the precision of whatever control mechanism or joystick you are using to get the full scale of motion, so this should graph that to the new maximum:
Code:
long answer; //Must be long to hold precise values
if (p1_x > 127){ //Or whatever joystick
answer = p1_x * 200 / 255;
pwm02 = (unsigned char)answer; //Cast this to the proper type
} else {
pwm02 = p1_x;
}