tranny in park? my stick didn't have park as a choice.

if auto, then yes, in park. i wouldn't worry about the brake assist. you won't even feel the jeep back there*. in fact, you might even forget it, and back up while holding it.

it's been a while, but i'm thinking the comp got a "jet stage 2" module. a 62mm throttle body also went on. for the add-ons, i take what the manufacturer claims, then subtract 50% from their low number. if you add-on 40 hp worth of stuff, figure 15-20hp actual gains. opening up the exhaust is probably the single biggest benefit for the 4.0, short of a ported head and a cam.

* i never towed my jeep behind anything, i just towed with it. i've always sold a jeep, for more than i paid for it. they retain value if you take care of them, and use quality parts while keeping the factory take-offs in boxes.