I really don't want to debate egr., run it,don't run it IDC . It is there to reduce combustion temperature,allowing more timing,without detonation,it also reduces NOX, the additional timing,offsets the slower burn,from the egr diluted mixture. The additional throttle needed to pull a hill is to give it the fuel the egr is with holding that fuel you wete going to already be burning,with out the egr to offset it,and weren't going to climb the hill with or without egr without more throttle. The additional throttle angle reduces pumping losses,the engine turns over easier with the throttle open,as long as additional fuel isn't being consumed the higher thrittle angle is more efficient and increases mpg,EGR also increases mpg by partially filling the cylinder with a mixture other than fresh fuel and air,(its a glass half full thing)the increased timing increases mpg. Many engines will detonate badly if you disable egr. Those are things anyone can google and make up their own mind about.There's plenty of science and engineering to back it up.EGR was added as primitive engine management to reduce emissions but also to help meet CAFE (mpg)and octane demands.Manufacturers weren't just told cut emissions,they were told cut emissions,and bring up fuel economy.My own theory is a lot of the post EGR heads that are cracked, that everyone labels as bad castings,are caused by disabled EGR the extra heat and preignition I believe contributes to cracking the heads. And FWIW for years, maybe decades I hated EGR,I disabled EGR,and as I learned more about it and all the ways it works that we don't see and most don't know,I changed my opinion. If I buy something with disabled EGR I enable it tune it and go happily on with some extra mpgs and the ability to run cheap fuel