1994 Pontiac Bonneville Stalling around bends & gas mil

Hello - while driving around large bends such as an exit ramp, the car will stall out when the gas gauge reads around 1/4 tank full. I know it is because the gas is moving in the tank and not getting picked up by the pump properly but is this normal? My 89 Bonneville never did this no matter how low. Once I get around the bend, I put the car in park (not sure why I can't start in neutral) and it starts up. I also notice the car's fuel gauge appears to be off by almost 1/8 tank (is really empty when it shows 1/8) and the fuel efficiency is poor. The car had a new fuel pump replaced (was my parent's car) and I assume it was an OEM part as the dealer replaced but this problem did not exist before. The dealer told my mom the problem of stalling was due to baffles in the tank causing the fuel to not reach the pump but that seems a lame answer or else this situation would require a recall for safety (stalling on an exit ramp is a good way to get rear ended by a semi). As for the fuel economy, I didn't know if a bad fuel pump could cause poor gas mileage (I know there are a ton of things that could cause this and I am working on all the other things to help that). Thank you much for your assistance.