kevlar

i want to add hp, but do not want to spend alot of money or add to egt's. i currently tow about 5500lbs regularly and when i add my camper that would be an additional 2000lbs. i think the edge ez would be all i need. i dont know if it would be necessary to add 4" exhaust? also will the elbow that comes with the kit work with my jacobs exhaust brake? thanks for your responses