To quiet road noise and vibration there is Dynamat substitute you can get from lowes or Home Depot.
For exhaust sounds, a cheap muffler w/ silencer.
For engine noise you can tighten down your belts and make sure things are in good shape.
Also some common sense things like my hood latch would vibrate and my glove compartment would squeak. I put some black electrical tape around the hinges and now they're snug.