i never understood what they did

One, make sure you dont have E-check where you live...

Basically they eliminate the EGR (Exhaust Gas Recirculation) valve. When this component is not working correctly, very common in high mile vehicles, it can affect gas mileage and performance. It is also the main contributor to occasional cleaning of the throttle body. Essentially, its just an environmental component. It is illegal to remove it and drive with it blocked off, but generally it wont be checked until you got to get E-check done. Also, it will throw a code 32 - EGR valve failure- but it wont affect anything. That can be bypassed with the performance PCM

Hope this helps!

basically it does what it says

i think he means why use one like the benefits of getting it

could you get one

then take it off when you have emission and pass?

Yes, I suppose thats possible.. but it is a PITA to take off and put on!!

im gonna get a block off kit for my car soon so that i have more room for the intercooler piping

Yes or get a Mopar or AF/x PCM that doesn't look for it.

the mopar ecu isnt legal in california

and i live in california

so when i get smogged i have to reconnect the old one

i dont think i would be able to live sumwhere that had emissions testing or anything like that.....it would drive me nuts[:@]