I've noticed my engine bay is quite loud as well. And always wondered why it'* so loud. I used to work in an oil/tire/battery change shop and it seemed that most of the GM V6'* are loud like this. I was told by a person once who said that a lot of the noise comes from the upper intake since it'* plastic and allows a lot of noise to come through. It just seems that the GM 3.8, 3.1, 3.4 engines have a lot of rocker arm noise. they always seem to tap even with low mileage and in good condition. Sorry I don't have an answer but i hope to see an answer to this as well.