Fuel : Return line vs Returnless
 

I had read some information abt fuel line
Engine Management - Electronic Fuel Injection

if not mistaken, our FIT is returnless with 50 PSI.
I was wonder what is the advantage of fuel with regulator and return line
if consider that I had TD04 turbo?

By reading my AFR gauge, I still able to reach 11.6 : 1

because
1 of the workshop asked me to modify with fuel regulator type.
I still consider should i spend this $$ or safe it?