Knock knock go away/is this the norm on a 4cyl?

okay i got the tension pulley fixed in my caravan now when im idle i here a flapping or a spitting in the engine area and when i am in motion a knock not real loud but as i accelerate it gets faster too ive changed the spark plugs and the PVC valve i do have a e vap leak that shows up on a scan but i don't think that would cause this sound its a 2001 4 cyl. dodge caravan with 91,000 miles oh i read the gap instrucyions on my van it said 50 so i did spead the gap to 50 on my sparkplugs.oh yah and im told this sound is normal for 4cyl,s with over 80,000 miles is there any truth in that.