[old_tv_nut]

The reponse at the "new test point" (top of color level control) confuses me. If it is supposed to control color level, its peak effect (due to L18 resonance) should be at 3.58, in my opinion. I can't understand why they would want the symmetry of the response to change with color level setting.

Try this: change your test point to the cathode of the second amp (pin 6 above the 150 ohm) and turn the color level to max to take L18 out of action. See what the response is and what effect tuning L17 has. Then maybe we can go from there.