Crankcase evacuation kit!?

I've run them on my car with mufflers. They do work with mufflers - in proportion to the amount of back pressure your mufflers develop. I ran delta 50s on mine for some time and the back pressure caused the check valve to fail prematurely. Just changed to some straight through Dynomax glass packs and new check valves and have lots of vacuum on them now. If you run tghem with mufflers use a straight through type of muffler - and with any type check the valves function periodicly. All you need to do is to pull the line off while the car is at idle and you can tell when a valve is shot.