Helps if you know vehicle weight,gearing carb calibration actual mechanical compression & camshaft overlap.I originally remember this,to reduce NOx... High temp combustion temps raise this, overlap /egr actually cool it down. In actuality ,egr can richen an over lean OEM carb set up., The government & lack of compression & driveability makes it a necessity on non F.I. cars.https://www.google.com/url?sa=t&sou...GIwlCJdR_vJKyqzOg&sig2=sjNR3qlIO8qGJuHIA1hJcg
