Today, driving approximately 30 mph, the car stalled while driving over a bridge. This also happened rather recently. The drive belt and drive belt tensioner were just replaced about 3k miles ago. The car has also been running kind of poorly lately with a loss in fuel economy and the economy gauge does not go all the way to the left at idle (it is stuck about 1/4 of the way towards the right). I was wondering if any diagnosis can be made based on these symptoms or if anyone has any ideas.
Thanks much
Ben

PS I was thinking of vacuum leaks, a bad battery, and/or bad injectors or seals as the likely culprit. I hope it is not anything like a fuel pump fuel pressure regulator. any ideas on this one?

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currently just 1989 300SE 185k miles