MyPCV hoses and clamps were a bit loose. This could become a vacuum leak if left alone. The hoses weren't cracked so I just got new hose clamps. I also was going to replace the oil cap seal but a new cap is only a little more than a seal. TRD has a $$$ oil cap. I am sure that it will add 30+ hp to my 1FZ but not worth the extra $ I replace the spark plug seal when I had the valve cover off along with the valve cover gasket. This should stop at least any vacuum leak from the valve cover. I bet the valve cover seals/gaskets would be one passed over looking for a vacuum leak. kurt Just remove the oil cap whe the motor is runnung and see what it does??????????