Rotel Tuner RT-935AX : How to Mod ?

[bordins]

I am trying to mod my Rotel tuner, RT-935AX, to make it FM selectivity better. I found interference between stations is quite strong. Unfortunately, this tuner doesn't come with the narrow FM band select switch.

There are several tuning knobs inside the unit. I wish I could know how to tune them. Any one could point me to any information source.

Thank you.