How often should you clean the injen intake? What is the best filter to replace it with?

I would say clean it probably every 8-12k miles. I would keep the filter it came with, on there.

depending on driving conditions... i mean are you in a dusty area or moderate city driving? it varies per your location... maybe rule of thumb every 8-10k?

i just slightly rub my hand over the filter... if there's a lot of dirt and residue, then it's time to clean... if it's not too bad, then the filter should be ok... also, you can tell by color. typically the filter should be a magenta/fuscia (that's right, i said fuscia) color, but if begins to turn black, there's too much dirt.

also, after you're done cleaning and ready to reapply the oil, if it's too pale in color, somewhat pinkish, then you need more oil on it.