2003 Mustang 3.6L 130,000 miles. Squeals obnoxiously after I crank it. I'm told it may be the water pump?? But this isn't what really concerns me, what concerns me is that whenever I drive it, it seems to hesitate, and jump... At low RPMs. It feels like it isn't getting gas... I don't know what may be causing this... Yesterday when it started jumping, I filled it up, and the problem seemed to vanish until later last night... I'm a new driver, so something like this is pretty scary. Any help would be appreciated.