by recirculating exhaust gases into the engine. How can hot exhaust gases lessen the chanceof detonation you ask? Because its not oxygen rich so there's nothing to burn. Now, do I think it's really that big of a deal......mmmm dunno. There are a few ppl here who have done it and I personally havent heard of any negative feedback, but I could have just missed it. I do know you will need an oil catch can if you plug the ERG tho......just FYI.