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Phil's response is correct for the 5M when under vacuum.

On the Mk3 Turbos, Toyota also added a RRFPR with a 1:1 ratio. That way, the effective fuel pressure doesn't drop when the engine goes into boost.
Imagine if it weren't there. Lets just say that fuel pressure is 38 psi in the Mk3, I have no idea what it really is. When the Mk3 gets to 12 psi of boost in the intake plenum, the fuel pressure would effectively be only 38-12 = 26 psi, causing engine to run lean. Adding that 1:1 RRFPR keeps it at 38 psi all the time.
For the Mk2, 1:1 RRFPR is definitely not enough. By my calculations, you need a 6.5:1 ratio.
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