EVR question.

I did a search on this as I know there are alot of questions relating to the EGR and EVR but didnt find what I was after exactly.

Ok.. So I noticed something today while removing the remnants of the smog system. I was relocating the EVR to a more convenient spot and noticed the cap on the bottom was gone. Dont know how but its just not there anymore. This exposed a small metal tube.

So, I started my truck and let it idle and went back to the EVR and felt the end of the metal tube.. It had flow, so I plugged it with my finger. My truck stuttered, the idle dropped and it sat idling like crap as long as the tube was plugged with my finger. As soon as I removed my finger the idle jumped back up and held normally.

So what function does that cap accomplish? Im guessing it allows some kind of buildup of vaccum or pressure or something? It certainly doesnt seal the tube (I hope anyway.. my trucks running poorly enough as it is, I dont need it to run any worse.. lol). Is it there to allow some kind of buildup of pressure or vacuum or whatever?

Thanks much.

Yeah, I checked the EGR's vac line and it doesnt get any vac at idle. I was just curious as to the function of that cap on EVR, which seems to be minimal.. Just used as a filter.

That lets me cross one more thing off my list of crap that could be causing my issues. Hopefully when I get my timing light (bought one today but it was broken and wouldnt work =/) I'll be able to track down my miss(s)