Im not 100% sure on what the part is called but located on the Passenger fender just under the hood looks like a Vacuum switching box with the 3 lines running to it. I cant find any info on it, Although I do Remember Posting about it a while back, still foggy on what it is called, But that was what was making it backfire "all the time" on top of the plugs, I must have forced the new line too much after I pulled the box from a parts Trooper we have, and when I ran new hose for it, over stressed it so it led to a break, It Idles smoother now, runs great. Doesnt want to bog down when I floor it since I have changed the Gap on the Plugs and that Box as well. So Im assuming that with the new gap set on the plugs and that line fixed it solved the Mystery Pops. Now the ONLY time it backfires is when its really cold out here in Wyoming and its first started and then Driven soon after. (Ahem, this is WITH NO cat. Converter BTW Ahem)