Farting bass sound? How to rid myself of it.

Get fatter strings.
It sounds like the strings are flying all around the place.
 
If the bass has an active EQ, leave it flat, or even turn the bass down

If you want to get a good driven bass tone, copy the bass part, and use one for a clean bass tone, and another for dirty. Highpass the dirty bass tone, as any low frequencies will get really muddy when distorted.

And... MOTHERFUCKING HIT those strings! :D