LS engines have a strong flow of air in and out of their crankcase for the PCV (Positive Crankcase Ventilation) system. The PCV is routed back into the intake manifold. If the air flowing out of the crankcase contains oil, it ends up inside the intake manifold where it puddles up and eventually gets sucked into the cylinders and burned. The amount of oil in the PCV air varies by the condition of the engine (piston rings, mostly) and by how it's driven.
The routing of the PCV is that it comes out of the driver's side rocker cover, through a hose and into the top center of the intake manifold. The catch can is simply placed inline in this circuit. So, the routing would be out of the rocker cover and into the catch can, then out of the catch can and into the intake manifold. It's just an inline filter.
If you don't do a lot of high-load driving, then your engine will likely not pass much oil through the system. High load is not just hard throttle and high RPM, it's also moderate throttle and lower RPM, such as when going up an incline with just enough throttle to keep it moving but not downshift. This is also known as "lugging". The engine makes a deeper growl during this- I'm sure you've heard it. Having only 4 speeds to pick through, it'll happen more often than with a vehicle with more gears. It's fine for normal, everyday driving. But, a custom tune will improve these characteristics and make the vehicle more responsive. The factory programming is geared towards fuel economy and soft shifts at the expense of throttle response and trans life. Even the 6-speed transmissions benefit from better tuning.
If you wanted to prioritize these three mods, I'd order them as disabling AFM then/and installing a catch can. That's maybe $100 in worthy mods. The rocker cover isn't so pressing due to your civil driving and the catch can will make up for not having the updated cover in some aspects. The updated cover and the catch can both prevent the oil from ending up in your intake manifold, but the cover will keep it inside the engine. The catch can collects what makes it out of the engine and you drain it and dump it or, if it's clean, pour it right back into the engine. The cover is bumped down the list because it's kinda pricey at something like $60-$70, you have to remove your current cover to see if you even have it and you can kinda make up for it with the catch can if you don't have it. But, you should still have it to keep the oil inside the engine and rely on the catch can for just what makes it past that updated cover. At least it can wait, maybe until you find a deal on a used one or something. If you get bored one day and wanna take the 30 minutes to remove your rocker cover to check, it would also have the benefit of giving you a glimpse of the level of cleanliness of the inside of your engine.
All of these are the few small and cheap mods that were mentioned earlier that would go a long way in preventing damage/wear/failure. They're literally the "ounce of prevention" that's worth a pound of cure.
