This is quite useful if you have an 87-90 YJ with the 258 and you swap to a weber or MC2100 carb. If you add a posi-lock, just cap the nipple where the 4wd connection is at the reservoir (shown in diagram as yellow line). Everything else that is not shown in this diagram can be removed (emissions related lines and such). This setup gives a nice balance and good idle on the 258. I did this on quite a few YJ's and all of them were very happy with this setup. There are other setups out there that may work too. I just know this one works with the 258/5 speed. If the auto tranny requires a vacuum connection then ymmv.
I came to find this setup from trial and error. I tried to keep as much of the original stuff as I could for a long time and it was just horrible. The jeep ran like crap until I ripped out everything else. I removed the BBD carb and replaced it with a Weber. I removed the stock ignition and replaced it with a junkyard HEI setup. I removed the complete emissions feedback tube and valve system and capped the port on the catalytic converter. I tested the EGR, the CTO, and the emissions canister before I re-used them. You can run without the EGR but it works fine with it and it seems smoother. The emissions system is now controlled by the Coolant Temperature Override (CTO) valve. The valve opens the EGR and the emissions canister purge when the coolant reaches the pre-determined temperature. This keeps the system from dumping the waste into the carb while the motor is warming up. Manifold vacuum is fed to the vacuum input ports on the CTO. When the CTO opens it allows vacuum to flow to the valve that opens the EGR and the valve on the canister. This allows the waste gas from the canister to be sucked into the intake and burned. You can test the EGR by removing it and applying vacuum to the port and see if it opens. You can test the canister by applying vacuum to the signal port and then sucking on the output line to see if gas passes (warning this can be nasty - LOL). You can test the CTO by placing it in a pan of boiling water (with vacuum and output lines on it) and sucking on the output lines (one at a time) to see if they are open. Make sure your lines don't leak or you will suck boiling water through them. You may want to have a buddy apply the vacuum on those - LOL.
