Yea as far as I know the only "tool" is in Horizon & you have to be Diamond(paid). There's someone modding saves on here though. I had him do mine yesterday because the files I was using on my RGH kept messing up my save. Anyway, here's a link to his thread if you're interested. http://www.xpgamesaves.com/topic/57133-forza-horizon-service/page__p__267404#entry267404
my mate modded forza horizon on xbox, had 999,999,999 money, all the cars even from dlc but think he had a jtag xbox tho