Returnless
 

I have a 1998 1.8L MK2 MX-5 (Miata). It should have a returnless fuelsystem, but I see a fuel feed line and a fuel return line. The return line is attached to a vacuum valve. (FPR?)

You can see the two lines in this picture:
http://home.casema.nl/grashuis/images/KuroT6.JPG

A member of another forum suggested that only the 99+ Miata's in the US are returnless. But that doesn't make any sense to me.

I'm looking for a way to manage the fuel supply on my MK2 MX-5(Miata).

Atleast in the US, only the '99+ Miata's are returnless. If you have two fuel lines then you obviously don't have a returnless fuel system.

If you want some serious engine management then go Megasquirt.
If you want some bandaids then go FMU, Bipes O2 clamp.
Short summary of what you really would have to do.

I have a Greddy eManage Ultimate and 550cc injectors. But I'm also looking for a fuelpump upgrade and a Walbro doesn't work on a returnless system it seems.