I run octane booster anyway, I'm afaird of fuel quality at my boost level.

 

Put your vehicle on a dyno with a stock PCV system. Tune it.

Take off PCV system and vent to atmosphere. Run it again on the dyno and see if it can now take more timing. (Maybe an actual tuner can tell you what you would expect, I'm no tuner)

That should at least tell you if there is some effect. From there maybe some complicated maths, beyond my level, could help you answer your question.

 

Which booster do you use? Did you start using because of knock? I was running anywhere from 17-19psi (belt slip dependent) on my 4.8 and never thought about needing booster. Although I doubt timing was extreme I never remember having any knock. It certainly never tripped any codes.

 

I run Lucas it is safe for my cats. I get a little ping every now and then if I sit along time at light when it's over 80 ambient if I smash on it only though. The Lucas helps but it's pricey.

 

I need a catch can that stops the oil I burn off that's on the cylinder walls


I can see everyone's point of view here. They aren't for me really and my builds and vehicles I work on/own/build. I have worked on 3+ cars a day on average for over 20 years, had several very hard ran engines in cars trucks boats motorcycles etc, nitrous, turbo and all motor setups, not a single one with a catch can on it, and not a single one of those thousands and thousands of engines has ever suffered engine damage due to not having a catch can.

OP I love your math breakdown about the amount of gas vs oil and the percentage breakdown. That really is a great point.

Atomic has a good point too, a engine running on the edge of safety needs every single bit of insurance you can give it, so give it a catch can.

Are there some cases where they are useful? Yes. Are they needed for everyone? No.