I've done more than a few now and not only Nissan. Key is to remove and replace ALL old hoses and Re-seal everything.. Oil pan - valve covers etc. Run a couple cans of engine and coolant flush thru it once running. In a couple of weeks it should smooth out.. This was the advice I received from some very good auto specialist in different parts of the country. So you can add the extra cost for removing the old parts and re-sealing also a great time to clean throttle bodies, upper and lower intake.. Seems most guys are toooo cheap to do the added precations.
