So I have a '12 Silverado with a 6.2L that I recently installed a cheap catch can on. Well the catch can leaked so it started throwing lean codes. I sealed up the catch can fittings with RTV, and confirmed it was sealed with a pressure test but I still kept getting the same lean codes. So tried I bypassing the catch can and the codes still came back. I then removed the factory quick connect fitting from the driverside valve cover and put the hose directly onto the nipple and clamped it but it's still leaking. In fact I can hear it whistling! I can pinch the hose all the way right up to the valve cover and the whistling goes away. So figured the hose wasn't sealing on the nipple so I swapped back to the original quick connect fitting. Same whistling. I'm out of options here, could the PCV valve inside the valve cover be bad causing the vacuum leak?

I do want to add that the catch does work and it has been catching oil. Here's what my install looks like:

 

It's hard to say without a close up of the suspected fitting/connection. Is it possible the intake is cracked around that fitting or needs some thread tape? I'm not certain how that interfaces with the manifold.

 

Ok, I have nothing to add yet except that I have that EXACT can on my Buick, and I too have a vacuum leak. I welded -8 fittings to mine, and have it routed differently. I also replaced nearly every gasket on that motor when I bought the car, so I can't say the can is the problem, but now I am curious.

 

The connection at the manifold just pushes in and has some lock tabs and an oring that seals it but I think my problem lies at the other connection at the valve cover. If my leak were elsewhere then my pinching off the hose wouldn't stop the leak.

It's a decent can for the price but it's not turnkey. Mine leaked at each port and the dipstick so I put some rtv on the threads and an oring on the dipstick. Either way still way better than spending $300+ on a slightly nicer one.