Audi A8 Tank fuel pump runs out of fuel at half tank

Hard to make this brief. HA! a common problem- yet does have a repair kit available from V12 throttle.com. And advise from TraditionpartsAudi. The tank pump is a two outlet: one pickup electric scavenge fuel pump fit in a plastic basket in the tank. Its job is to send fuel to the engine bay mounted FI fuel pump. Mounted side-saddle to the plastic tank pump housing is a "Baffle" box that has an open top as viewed from above, (SEEN in VIDEO) . This Baffle box received fuel from three "scavenging vortex amplified accumulators", one located under and close to the fuel pump, and the other two extended out to the ends of the horseshoe-shaped black plastic fuel tank. Each "Vortex Accumulator" uses fuel pressure delivered from the bottom spigot of the fuel pump to force fuel through a nozzle and through a funnel shape that tends to accumulate MORE volume of surrounding fuel and deliver it to the "Baffle" box and thus also to the Fuel pump basket that is otherwise isolated from the ambient tank fuel that it is immersed in due to fuel pump basket having ONLY vortex picked up fuel available **. (Stupid?) an unavoidable design element to scavenge all tank fuel and deliver to the fuel pump basket. PROBLEM= the Vortex system is inefficient and not a closed loop--eventually running out of nozzle fuel to keep the vortex operational as the tank pump empties the fuel basket eventually ( 2.5 minutes). The fuel injection pump at front of vehicle has a return line for excess unused-by-injectors-fuel. ** The FI pump's return line at the tank is at the top of the opening to the fuel basket next to the baffle box and ** ALSO fills the fuel pump basket. Without this return line supplying the isolated fuel pump basket, you simply run out of gas at half tank. Otherwise a full tank overflows into the basket and keep you going until the level is too low for basket refill by vortex accumulators alone. A bit complex. Essentially, our problem was a hole in the vortex pressure line that disallowed refill of the fuel pump basket over time- eventual starving the tank pump. We hope this helps. Other input important. Reply to the video if you have more info. We tested without the FI forward pump in circuit by recirculating - see clear hose. It made sense to us. We do not have the vehicle, only the tank.