did you replace the gasket or the lower plate with the aluminum plate? If you replaced just the gasket it won't last very long at all. I'd go after the pcv valve next. I replaced the plate on my 99 5.9 2500 and it still used a small amount until I replaced the pcv valve. I did buy the aluminum plate and install on mine. I've seen new gaskets leaking with as few as 100 miles on them. The problem is the plate, not the gasket.