Okay, Hijack v337 will have a menu entry for "Tuner AF Blocking" -- toggle it to "Enabled" to try blocking the AF functionality. I think that this will also block ALL RDS functionality, but am just guessing at this point.

It can be changed on the fly, without rebooting, so you can turn it on/off for testing purposes. I have no idea whether it actually works or not.

It'll be about 10 minutes or so (from this message being posted) until Hijack v337 appears on the website.

Cheers