The rack dampener adjustment is so very easy to do, you should probably consider it as the first thing to tackle here. There is a long list of things that can cause what you have decribed, this can be the easiest to solve.
I am not sure replacing those mounts under the air cleaner will improve your problems with the rattles, unless one of them is broke. Then it will rattle loudly. One of the members suggested that he was able to stop the air cleaner from rattling into the valve cover by using an old isolator, and drilling a hole into the left side of the canister about where it rattles into the valve cover. He then just bolted the isolator into the air canister so that it would prevent the canister from stiking the valve cover. I tried that and it works well, and did not cost much.
But first thing there is to check for any broken, torn isolaters.