Where do you have the receiver mounted on this car? When I had my XXXS, which is not much different then the XXX4, I mounted my receiver on my speedo and made sure the antenna wire did not touch the chassis at all. If it was going to touch the chassis I just ran a piece of fuel tubing over the wire so that insulated it from the chassis. Why can't you run Spektrum on this car? Just no money for the receiver?
JRXS Type R, I have four of them!! ;) ( Yes, I still have them!!)