Ok so when I came back to TF2 after a took a few good months off, I had a welcome present which was a wave of lagging nonstop (this was when the NYC update came out). I resolved this issue by deleting a butt ton of files in my TF2 folder and putting something in the launch options so when you boot up TF2, it starts up as if it's the first time ever. This resolved every issue I had and back to 60fps. I will come back to you and tell you how I did it.