This is gonna be one mentally quick rod

its definitely coming from the engine starts at aout 2500 to 5000 over that its normal

Hi can anyone tell me what the noise coming from my engine is? Its making a groaning\rattling noise which only occurs between 2500 to 4500 revs. The engine is not down on power and it pulls cleanly in all gears. Any ideas. Also if this question has come up before i apologise i've just joined the for...