I've been on a 3.0 for about 5 months. Regularly making anywhere from 13 to 15 psi. I went to a 2.8 for a few days for testing and saw a little knock (this was two weeks ago) and hit 16-17 psi. People have run this setup long term. I saw knock so I went back to a 3.0 but I wouldn't hesitate to run a 2.8 and hit 16 or 17 psi daily. If your car is running well, do it.