Depends......
As in - what kind of tank it is - and who built it. Without that info nobody could answer that kind of a question. Stock factory tanks had no baffles... including the SS replacement versions. Rock Valley and Ricks Tanks etc - would be baffled. Baffles would take care of fuel SLOSH... they DO NOT take care of cavitation at the intake caused by a lack of coverage.
EFI draws large amounts of fuel at all times... Think "toilet bowl flush". Fuel boils under suction... so the supply lines to the pump need to be sized for the application... and they need a nice clean flooded "head" for supply. Think -10 AN for the supply side MINIMUM. A SUMP helps to keep the supply flooded. It needs to be at the rear and bottom of the tank (unless you're internally sumped and baffled). You need adequate fuel going UP HILL and when you're accelerating hard. You don't need much coasting downhill or just cruising on a level street. EFI will not run on air bubbles and fumes... there's no pressure made in that instance. You can use your existing supply line as the return. Again depending on the proper size for the application. If you're planning a 900 HP blown EFI motor -- the factory line would be totally inadequate.
