How often should the Injen intake (or anyt intake) be cleaned? What is a good way to clean it? Does it need to be oiled?

Do you mean the filter? Or the actual intake? The filter should be cleaned whenever its dirty. Mine isn't protected the way it should be right now so it gets dirty fast. I clean it every couple months. With a shortram like the injen, you should be able to do it a couple times a year and be ok. As far as the intake tube goes, I'd just take it off and wash it with soap and water whenever you clean the filter.

I'd be more worried about cleaning the throttle body. thats where a lot of the gunk ends up. >>

Yeah, not a bad idea but I put the most emphasis on the filter. If its clean and working well, then the throttle body shouldn't be that dirty.