Fuel Return: Adapting Properly
The MR2 comes stock with a fuel return system, which must be addressed by either installing the pump from the source car into the gas tank, tapping the fuel rail to accomodate the return line, or obtaining a fuel rail from a 3VZ-FE which is a direct fit.
3VZ-FE Option
“This is old news to Camry guys but a 3VZ-FE return fuel rail system will bolt right on to 1MZ-FE. this set up gives you the regulator, lines etc.. just bolt on. you can probably get one from junk /core motor at a yard for cheap. …if you have a turbo and still have fuel line it will bolt right up. otherwise (non-Turbo owners) you will have to have new hose crimped on. The rails from a 94-96 1MZ-FE will have full return style system and your MR2 return line plugs right in.
…if you are a little unsure about tapping stock 1MZ-FE rail i would highly reccommend the 3VZ-FE rail install…save time and will be 100% OEM.” -derek2000GT
Tapping the Rail Option
“The fuel rails are fine if you do not want a return system, but you will have to have a fuel pump with a FPR or an in tank FPR like a Camry, as the 3S-GTE has an FPR on the fuel rail in the return system. I have an adjustable FPR (AEM) on one of my fuel rails for when I go to larger injectors. I bored out the end of the stock rails, threaded them on the outside, and connected them with NPT fittings to the MR2 system.” -chall
I have used the earlier fuel rails and also welded -6 lines with an adjustable regulator for my two cars.