I can tell you right now what it (more than likely) is -
When you're on in an incline, the back of the front fender will be dipping down more than a flat ride, which will cause your tire to rub on the bottom of the metal fender (or if your plastic wheel well is lower than that). What you'll have to do is called a Norcal mod.
If you don't want to trim your metal, then drill a few holes in your plastic wheel well and ziptie it as tight as you can to pull it as far away from the tire as possible.
Other thing it might be is your traction control. Lots of guys on here have warned me about my zip tied ABS wiring to my knuckle and that's what was causing my grinding/slowing down of the truck randomly when turning or going down hills/up hills.
And as for watching the tires go to full lock... Just remember, your X amount of weight when sitting in the drivers seat makes the suspension drop a fair bit. So when you're standing outside of the truck with no one in it while watching for rubbing, that won't give you an accurate visual of how the suspension actually sits when driving.
Just keep in mind, your new suspension lift won't sit at the 7.5 inches for very long. I've had the same lift on my truck for 1.5months and I've already had to trim more of the valance off because the suspension is settling.