I never had diff issue's with my XTM's(same as firehammer) but I did have motor mount issue's with it, the fg's have the same issue, plastic motor mounts aren't just made to hold a gasoline engine down, they arent actually cheap parts either. Once the mounts got replaced though it was alright, but it's not like a hpi baja thats for sure it's far less nimble and far more prone to breaking and very limited on jumping.
I'd never get involved in gas cars with a limited budget, actually anything in this hobby is bad news if you're on a limited budget, they all require some sort of cash sunk into them...rc's are almost like the irs, just their hand isn't in your pocket as much but it's in there enough.