So are the S4 and S5 fuel pump assemblies interchangeable?? I've got an S5 vert with a TII swap, it had the NA fuel pump assembly. I installed a Haltech about a year and a half ago, so I modified the stock S5 NA fuel pump assembly for the rewiring of the fuel pump. I have an S4 NA fuel pump assembly, so I'm wondering if I can use that one instead of the S5 NA fuel pump assembly? Thanks!