BruceTF135

My 2004 TF 135 is a bit tappety when I start it up. I don't use the car as often as I should so maybe it is just the oil draining down. The tapping disappears as the engine warms up. As it has done 112,000 miles I'm thinking of using some valve lifter additive. Is it worth doing or is this stuff ineffectual? If I'm going to use it, is it best to put it in after an oil change or to put it in and run it for a while before the oil change?