Starlet Ep80 Rear Break Problems

[EP´s]

Hi menbers,

I´m having troubles with my starlet 1000 EP80 (1992) rear breaks.

Its the first time this happened, the right rear wheel its not breaking properly, breaks less 47% than the rear left.

This happens only with service break (pedal brak) with the hand break its braking very good, only 1% difference between rear whell

sI changed both shoes, both cylinder boby and drain all the oil system by the Right rear wheel, the oil run free.

A friend told about the proportioning valve.

has this model a proportioning valve?

can it be responsible for this can be the proportioning valve?

I see a kind of spliter or 5 way connector afther the master cylinder where connects the pipes, its this the proportioning valve, can it control the oil pressure for each rear whell or its just an normal oil spliter.

thanks

Best regards