Does adding the mack rack plug alone do anything or do you have to mod the afc to get the benefits?

 

You will only get more rack travel if the AFC and plate allow it, so you will need to mod the AFC for travel (or gut it), and make sure the plate is deep enough to give you the full travel.

 

not to hijack, but how deep does the plate need to be to get full travel? I ground mine to what i would consider a shallow 100. I should be getting my rack plug tomorrow and i'm gonna try to put it in this weekend and also mod my afc. Its gutted right now and its ok like that and I can drive it pretty decently like that, but its easy to forget about it and then i end up blocking out the sun or the headlights behind me. I will miss having it gutted for those pesky tailgaters though...