Is it worthwhile to replace old manifold hoses to prevent vacuum leaks?

 

Try replacing your PCV valve first. It's cheap and if it's not working properly, it will cause what appears to be a vacuum leak. Despite it pulling in metered air, it's also pulling in oil vapor which has a very low octane and can cause detonation where none previously existed.

 

I pulled the big hose leading from the PCV to the intake manifold. There’s a little pool of oil at the manifold nipple and lining the hose, so there seems to be excessive oil coming from the PCV. The dipstick is reading about 1/8” above the second mark, so it’s a little overfilled as well. There’s a drop in K&N filter that seems to have a lot of oil at the bottom, and there’s a decent oil film in the air box before the filter. Not sure where that would have come from. I’ll be replacing the K&N when I buy the PCV parts and change the oil. Am I on the right track?

 

Yes. It helps to clean up any liquid oil in the intake for sure too.