CJ2A Exhausted!

My CJ2A stinks! After a short trip you smell of exhaust fumes. I usually drive it with no roof or doors (I don't have any!) and with the windshield up and vent open. When I bought the CJ it already had a shiny new exhaust system, I checked it through and found no leaks. I also went through and sealed up all holes in the firewall and tub etc but no difference.
I finally found some forum posts about exhaust recirculating back over the tailgate due to a low pressure area so I grabbed a 45 degree elbow and stuck it on the tail pipe which directed the exhaust out the side behind the rear wheel and downwards and problem gone away.
I guess my question is do they just do this with standard original exhaust systems or is my installation not correct?
Looking at picture is seems like my installation is close to correct. The tail pipe exits the rear corner but is not angles downwards. The pictures I have seen show it angled slightly downwards but is that enough to make a difference?

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About 1944 my dad had a jeep with a home made cab. I rode in the back and I got a first hand account on how the Jewish people felt while riding in a van driven by the gastapo. It is a wonder I did not pass out. Too stupid to know the cause. Yes, fumes are sucked up and will fill the Jeep. All Jeeps I have had I made sure the exhaust was designed to prevent this.

Most exhaust kits I've seen do angle down to pass under the quarter panel. A lesson learned on our wagon, do not drive around with the upper tail gate up, and duel exhaust exiting straight out the back.