RTV stands for "room temperature vulcanizing" and generally consists of a silicon gel that you apply to the surfaces you want to keep sealed. There is a variety so you can get the best type for the application- high temp, more adhesion, etc..,
Yes we have a factory catch can on our cars - sort of. When discussing catch cans you're trying to diminish the amount of harmful vapors that get recycled thru the motor and, over time, cause deposits to build up in places that can cause problems.
There is a "clean side" which uses the vacuum the engine creates in the intake manifold to pull the vapor of any unburned hydrocarbons (gas fumes) out of the top of the engine- above the valves IOW. Chevy provided a nice little black plastic container inline to catch anything that might try to rain out in the IM. That line then connects to the air intake tube for the fumes to be drawn into the engine. There's not a lot nasty stuff to be caught on this route. I've checked mine a couple of times since I got the car and never found anything there, but it's good to keep those unburned fumes out of the air we breath. Trochoidal has his still hooked up as well- its the front hose of the 2 larger bore black hoses at the front of the engine cover.
The "dirty side" also uses the IM vacuum and pulls vapor from the engine crankcase before returning it directly to the IM. These vapors consist of more oil, water, and other post-combustion stuff that the manufacturer wants the engine to get rid of. Unfortunately, with our incredible direct injection motors this can lead to the deposits and possible loss of performance or drivability issues over time.
That's where the catch can comes in. Placed inline with the dirty side, it provides a spot for vapors to cool, coalesce ( go on, look it up. I'll wait-LOL) and be stored for later disposal. If the location you choose causes problems due to future mods, it's an easy thing to buy more tubing and move to a better location. On a 5th Gen I had previously, a Vortech install required me to move the catch can down in front of the engine by the radiator. The resulting cooler location provided a huge increase in water (normal combustion by-product) collection. It wouldn't have harmed the motor by itself, but was sufficient to have possibly diluted the fuel octane... maybe, who knows but a catch can can give you some peace of mind. Have fun!
