I guess it's all personal preference, the catch can definitely won't hurt anything, mine has been running as is without one and I surely don't have black tail pipes like I did before the delete. I'm going to keep mine absolutely the same just to be a Guinea pig and see what and when will fail first. So far everything is working as intended.

And as far as the $100 vs $15 catch can goes, the Mishimoto one is very well engineered with internal baffles that are very good at separating oil from air vapors. They are a very popular upgrade with the BMW N54 crowd.

ok the way i'm going to do mine is take the drain plug out from the bottom of catch can put a on and off valve then at other end a hose running to oil dipstick tube so when can is full i open valve the oil drains back to engine just my thoughts simpler way of getting rid of the oil look at pic of sample valve

I don't think that is a good idea. You don't want to put the oil water mix back into the engine. The oil stays a lot cleaner with the catch can. You will see for yourself the first time you drain it!

I wouldn`t do that at all and contaminate the oil. you will be putting more water than oil back in not good.

lets think for a minute if the main objective of this mod is to eliminate the milkie build up which comes from condensation there should be no condensation compare to with ccv. all the pics that guys have posted of the oil after they drain the can not one mention about water in the oil especially with the higher vacuum condensation is only in the winter haven't seen it in the summer i could be wrong but that's what i'm seen

winter time is where I get a lot of water in the catch can .its a smaller catch can but im emptying it twice a month 90% water 10% blow by oil. so I wouldn`t want water dumping into the oil
summer time I hardley see any water. its the winter especially here with -20c on average through out the winter.

looking on more info to the water part i had it and now can't find the page damm

Resurrection
 

I'm glad you did dredge it up. A) Keeps the discussion to one thread. B) I'm learnding a lot!

E53 mod?
 

While it is too late for mine, is this something that could be done on an E53?

My apologies if that's an ignorant question.

yes, I just did this to mine, it can be done to anything with an m54 (3.0 )