Elaborate more on when the vehicle stalls out. Is it traveling on the highway under load, or is it at minimal throttle when it stalls.

Seriously, have you looked to check for bubbles in your fuel lines? That is the first and easiest item to check.

How is the performance of the car, does it seem underpowered or same as usual?

I think these main items might help us help you to track down your problem...

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'97 E300
'99 E300