Engine miss

My Volkwagen Passat (2003) will be hard to start and will miss if it is parked slightly downhill with about 12 gals of gas in it (capacity is about 14 gal I think). Is this normal with low gas level or should I try a gasoline additive for possible water contamination or is there another issue at work here. Thanks.

let me get this straight. If and only if you park it facing downhill with 12 gal of fuel (exact?) will it fail to start? So no problem with full tank or half tank? Why do you call 12 gal a low gas level, to me 2 gal is low?

If you had this problem with 1-2 gal in the tank, I could see water in the tank or some other contamination, but not at an almost full tank.

It could be normal on a low level of gasoline. Park uphill and I don’t know.

12 gallons of gas in a 14 gallon system is not low.

But the symptoms sound like a fuel delivery problem, so I’d be inclined to start by checking things like possible stored codes, fuel pump pressure, fuel filter, stuff like that.