Dave21 - did you ever find out what was causing your problem? I have an '07 GMC Duramax that is doing the same thing. One minute it'* running fine and then, it starts to stutter and dies,throwing a P0191 code. This usually happens when I'm decellerating. If I try to start it, it acts like it'* out of fuel and it won't run. Sometimes, it will start up after cranking and then it goes into the "limp" mode and you can't accelerate beyond about 5 MPH. The engine then sounds funny, like the timing has changed. I've had it into the dealer 5 times and they can't seem to fix it. They changed the fuel filter housing first with no luck. Then, they changed the fuel pressure regulator sensor. Again, no luck - it stalled again within 3 hours of leaving the dealership. Now, they have some kind of monitor plugged into the OBD port and I'm driving it, hoping that it will fail. Hopefully, this thing will record whatever is causing the problem and give them a better idea what'* going on. The dealer has been real good and has done everything under the warranty. I think, however, they're getting tired of working on it. Any help you or anyone else out there can provide would be greatly appreciated.