Hickup or spudder

I have an 87 audi 5000 2.2 liter manual trans and 175000 miles. I just got this car and have had it fror 2 weeks. When driving at aprox 2800 RPM's the engine will sometimes hickup or sputter as if gas is if the flow of gas is very briefly inturpted. Could this be just a fule filter? The car has no leaks and had a recent tune up, although I saw nothing about a new fuel filter. Also recently, again when I am traveling (usually on the freeway) a noise will sound very quickly and short like the squeel of a loose belt. But the belts all appear to be tight. What might this be? It doesn't appear to be related to the fuel problem however I'm not ruling it out. Any suggestions? Thanks for your help!