My 1998 Audi A4 2.8 Quatro is doing the following (and driving me nuts!). Run it for awhile, looses power, dies, wont start. Let sit for a few hours, starts, runs for awhile, dies, wont start. This is with about 1/3 tank. Fill the tank, starts, runs fine. This car had the fuel pump replaced (OEM pump) about 25 K ago. Any ideas??

Thanks!