hi ive just noticed about 1 month ago when my car is on idle its making a clicking sound. When i rev it between idle and 2000rpm i can hear it more anything above that i cant hear it. Sometimes when i am driving and i nail it it makes the same sound but way louder. Ive checked my oil levels and there all good and the oil isnt old or dirty either. could it be something to do with the lifters or something im not sure? got any ideas?