89 300E
Car has always run on 91 octane gas, but when I accelerate hard on a freeway ramp, I get all sorts of knocking until I back off the pedal. Plugs looks good and clean, but knocking still there. I did try a bottle of octane boost once and it seems to help in both throttle response and the knocking. Any ideas how I can reduce or eliminate the knocking without putting in bottles of magic elixer?

thanks.