you can get the stock vacuum system to work if you dont want to buy anything else, its not hard to do. I have duals with turn downs infront of the axle. I used to like it, but now its too loud and fumes come back into the jeep sometimes. If I could do it all over again I would purchase headers that the collectors point straght down. That way I could cross over under the oil pan and run a single exhaust. That way there are no exhaust lines near the brake and fuel lines. Also its way cheaper because you only need one muffler and resonator (if you choose to have one).
87 YJ, 350 TPI, NV3500, NP241C, 35x12.50x17, SOA, 8.8LSD Warn 9.5XP