Hi Flying Arrow,
What it sounds like to me is that you guys don't have a ghost peak. If on three different samples, with three different methods you have something eluting with your compound every time, I would figure that the issue is not a ghost-peak and is actually involved somewhere else. If for every injection you perform the product elutes with an impurity, and this occurs with different samples, I'd assume that it came from somewhere up-stream like within your sample preparation or perhaps mobile-phase preparation. Whatever this contaminant is does it decrease with increasing washes, have you seen it increase upon injection? When you run the column with blank injections do you still see the ghost peak and/or is it depleting? Perhaps are you running an ionizable sample and you have an ion-pairing reagent that is attached to your analytes? Sorry I couldn't narrow this down further for you but hopefully someone will come along with a more concrete solution.
Tyler