After getting my muffler done i relized after how loud my enigine bay is. Is there anyway to cut down some of the noise thats coming from under the hood?

Some serpentine belts are louder than others. A Gatorback is probably quieter than something cheaper like a dayco or a drive-rite.

If you've gutted your air box it is probably louder. It'* designed to quiet the air sucking noise at the expense of air flow.

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.

I had same thing when I got my flowmaster muffler on. One of these days I'm just going to go ahead and lube up any pulley thats lube-able. Really, that'* the only thing that came to mind when I thought of how to fix all that noise.

One noise you can hear running cold is your IAC. It resembles the sound that a pulley makes before it'* about to seize lol, but it'* coming from the wrong side of the engine bay. Other than that, I just faintly hear the valvetrain and what I assume is the loud-arsed pulleys.