See, mine does this, and so do all my cars that I've ever owned. No way should you even contemplate being in 6th gear at 30mph, and even 4th is pushing it. That's very bad for the engine as you're putting a monumental amount of stress on it, so I'd stop doing that for a start.
Not trying to be funny or anything, but are you sure that there's any issue here? Maybe you're just noticing the fuel pump more, and this has now led you to think there's something wrong so you're trying to find fault where one doesn't exist? Dunno, just throwing an idea out there.