So far the couple times I've cleaned the Envoy's TB it was reasonably clean so I haven't done much "research" on installing a catch can. For reference I did save those two pictures I posted showing how the PCV system flowed.
My wife's SRX has the 3.6l V6. Excessive oil comsumption has plagued some of this engine family. So far at 55,000 miles her's is doing OK. However there's some schools of thought that point the finger to the PCV orfice and suggest drilling out one of the two holes with a 7/64" drill... which I've done. I don't know the orfice size on our I-6 but the SRX is fairly small. A neglected oil change could sludge up the engine and easily plug the orfice. Also I've seen photos of the 3.6l engine intake where the oil vapors are sucked in. Lots of burnt oil deposits which would be helped with a catch can. I like to make things using what's in the scrap box so I took an empty propane cylinder and made a catch can for her SRX. It's only been in service for a short time so I don't know how much oil vapors it will trap. Some of the reading I did suggested the $20 ebay units don't have internal baffles and aren't too effective. Truthfully I have no personal experience. I do know there's a big cost disperity from high to low.