Answering from for sale thread.............. If your running this intake your trying to make more power obviously, emissions, smell, MPG, and performance shouldnt be in the same sentence. Evap simply takes vapors and puts them back in the intake to be re burnt. A common issue with NBS truck is that the evap systems has minor problems and needs repair. Its been nothing but a headache for me. So when I did my intake swap I took it all off. Behind the block agaist the fire wall i cut the line, and on top the intake where the solenoid goes i just threaded a screw in it to plug it off. I then used HP tuners to set it to not show CEL. So what i meant by that was is that you do not need it if you do not want to run it, dont want to mess with it, or having trouble with it. Also I didnt notice any smells but then again long tube headers without cats doesnt smell great anyway. Check my UC thread and you can see where I threaded a screw into the nipple to plug it off. Its just another option for those who have thoughts about not running it.