We use and recommend this relay harness for wiring in single or dual higher flow fuel pumps.
This harness was built with the BMW 3-series in mind. Wires are the correct length for trunk mounted battery with fuel pump under the rear seat.
The sealed relays and wiring makes for a clean and durable setup. We include a Deutsch connector kit that enables you to make this a plug-n-play setup. If you have two pumps, it's great for swapping power from one pump to the next to check function.