2004 Dodge Ram 04 Ram diesel with loud hydroboost

I have an '04 Ram 2500 w/ Cummins 5.9L diesel, auto matic 50,000 mile. There is a noise coming from the hydroboost. It gets a little louder when I step on the brakes and sounds kind of like the sound made when you blow across the top of a coke bottle. It's been there now for a couple of months but other than the noise the brakes work just find. To give you a little background, when I bought the truck 15,000 miles ago I had to replace the power steering pump because of a resevoir/pump interface leak. The hydroboost has only started make noise in the last 2,000 miles. Does the noise mean impending failure of the hydroboost or do they sometimes get noisy. (It's not a loud embaressing noise). And if it needs repacement, should I repace it right way to avoid brake failure or can I do it at my convienence?