[tbplus10]

Common issue with Suburbans. Summit had a high performance pump that was quieter, dont remember the manufacturer tho. Replacement pumps can be expensive to buy and a hassle to change, you might want to think how badly the noise bothers you before going this route. I have'nt tried it yet myself but I've been told you can get some insulation between the body and the top of the tank to quiet things down some.
The sluggish issue could be attributed to almost anything, most likely the engine threw a code and reacted to a sensor issue if it went away so easily. Go to Auto Zone and see if you can still get a code from the computer, this may lead you to the problem.