Make yourself a "sandwich" to go between the oil inlet on the turbo and your "-4 adaptor" with a hole in it similar in size to that of the banjo bolt that goes into the oil inlet on the stock turbo. Stacked in order you would have: turbo, gasket, new "sandwich" with restricter hole, gasket, original -4 adapter, two bolts. I'd make the new restrictor plate about 0.25" thick. Prolly take about 20 minutes to make. Just a thought. -Chuck
Edit: I was thinking I made the restrictor hole in mine about 1/8" dia. Best to measure if you have an old stock banjo bolt laying around tho.