[quote="Squeemish":17wk3hud]I thought you might be able to do this by adding something like, car.x > layout width, then set car.x to 0[/quote:17wk3hud]
You should use unbounded scrolling, but you should still have some kind of wrapping system like this: the further you get away from the 0,0 origin, the less accurate the floating point values that hold the coordinates become. Still, you can be fairly generous and have say 10-50k pixels before you wrap. You'll need it to be a multiple of the width of any tiled background images you use for it to be seamless.
Setting the X to 0 is going to stutter, because it makes no provision for how much further beyond the layout width you've gone (it still goes to X=0 even if you've gone 1 or 100 pixels over the edge). To fix this, subtract the layout width from the X co-ordinate instead, eg. Car.X > LayoutWidth, set Car X to .X - LayoutWidth.