here is a oil restrictor for Garret T series as they do not have built in restrictors ... opening is just under 1/16 ... a open 4/16 line, size of the opening on a typical Garret turbo oil feed, being gravity fed by a properly designed tank provides plenty of feed ... the real issues appears if it is not evacuated properly and positioning the tank right above the turbo ... otherwise use of one small pump to feed and one small pump to evacuate is in order (at least in a designing a separate oiling system from the engine).