Mechanic Q: Hi, i recently bought a 02 lexus is 300 manuel trans from a?

Hi, i recently bought a 02 lexus is 300 manuel trans from a car auction, and ever since i bought it, it always made this rattling or ticking noise comming from the engine once it hits 3000 RPMs, i changed the timming belt and also the clutch but the noise is still there, what can that noise be comming from? and around how much would it be to fix? thank you