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With the 350z, a return fuel system serves more purpose than in a 370z.

Return fuel systems with the 350z come in a few variations. There are entry level systems that are simply a conversion to return fuel, but do not improve flow on any of the feed plumbing.

There are only 2 reasons to convert to a return system of this style with the 350z/G35, and they do not have the same value in a 370z/G37.

1: Adjustable fuel pressure. Using an external regulator allows you to control exactly what your fuel pressure is. Not everyone needs this, but some people want it. When tuning cars with full standalones using speed density based fuel injection, or using piggy backs that add compensation fuel with their own speed density system (MAP addon), you can run into inconsistencies in the tune as environmental conditions change. In a full standalone this is technically avoidable within all the available correction parameters, but it can be difficuilt to dial those corrections in perfectly, especially when you are tuning the car under one specific set of conditions. You can only make educated assumptions how environmental conditions will change it. So to be able to adjust your pressure can, while not the most ideal, offer you a way to make a quick painless adjustment that will alter your end A/F ratios without having to get into the laptop. You would only do this for very minor adjustments, such as 1-2psi +/-. This is much less relevent in cars tuned 100% on MAF style fuel injection systems, which is what everyone is doing with the 370z (via UpRev reflash). The air metered through the MAF sensors is accurately and consistently precisely the volume of the air entering the engine with environmental conditions included. So unless you have come up with a specific reason that you need to change the fuel pressure, you arent really ever going to need to.

2: Vacuum referenced regulator. External regulators have the option to hook up a vacuum line. Using the vacuum reading, the regulator will add or remove fuel pressure in direct relation to manifold vacuum/pressure. This means at idle vacuum, the fuel pressure is lower. This also means that under boost, the fuel pressure is higher. This can make it easier to tune out larger injectors for idle, while still maintaining their potential on the top end under boost. However, this function is entirely irrelevent in the 370z due to the VVEL system choosing its own target manifold vacuum/pressure without direct correlation to engine load. This would make it an endless tuning nightmare as you will find your fuel pressure changing with no consistency outside when you are boosting. So you could not hook up the vacuum line to the regulator on the VVEL engine.

What all this means for the 370z; the advantages of simply performing a return fuel system conversion are entirely irrelevent. There is no advantage to altering the fuel system outside of pump or injectors, until the plumbing inbetween these points has become a restriction or starts to cause individual cylinder tuning grief as fuel will eventually bias cylinders when you start to push the plumbing too far.

The stock fuel system in the 370z has proven to flow more than adequately for any amount of power you are safe to generate on a stock engine. As a matter of fact, in my own car, I am using E85, which requires significantly more fuel quantity to acheive the same power... and I am still on stock plumbing.

I do not think anyone will have to worry about playing with the fuel system in this car (aside from pump upgrades and injectors) until they are at the point of requireing a second fuel pump.

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