On the 99+, the feed is to the rear of the fuel rail (yes, I know, the hose connects to the front but a tube goes to the rear and feeds the rail) so #4 feeds first. With my fuel rail, dual feeding is available but I don't think it is necessary as the stock rail is about 3/16" ID and mine is 3/8" ID. Cross section ratio is the square of the diameters so my rail is about 4 times larger. It will feed a LOT of fuel even single ended.