Single pass all the way. Only reason the multi pass is in there is because the OE pump couldnt move fluid through the circuit fast enough so you try to get it to spend more time in the there taking as much heat out as possible. Also remember that it originally was tied in with the engine cooling circuit so the objective was keeping the temp under 160 and having an easily maintained system vs what we are trying to do now and that is to get the intake charge as low as we can.