So does gc.buffer 2048 help? Type perf 6 or 7 in console (don't remember which) and it will give you a bunch of info on the bottom left of the screen to let you know if it's clearing garbage or not. Another thing that happens to me occasionally is that I think I'm having Rust lag issues when it's actually my internet. Any packet loss will make it seem like it's clearing garbage, while games like CSGO will run without you even knowing anything is wrong. I would suggest ping testing your ISP.

In command prompt type: ping www.google.com -t

Let it run for around 30 min and then press control+c and it will let you know your packet loss. You can see in real time if you're dropping packets, but it's easier to just let it run unless it's really bad and you can tell immediately. You can also find out exactly where in the network your dropping packets, but you will have to look that one up. It's almost never Google, but it's possible.