Putting on a larger exhaust, it lowers your EGT'S which is the heat coming out of the exhaust. To lower you egt's what is happening is the air is flowing threw freely that part is correct. The part that they don't tell you is the cam in this engine, the exhaust system, and the turbo is all built to maximize the pressure of air in the cylinder. The more air in the cylinder, the more fuel you can put in without smoke. Smoke only cools the cylinder pressure and heat that slows the turbo lowering boost. Without smoke the turbo gets maximum amount of volume change, that is what powers the turbo, and keeps the turbine clean which gives you maximum turbine speed. When I use to build Gas engine's for people, to get max HP and torque a buddy of mine had a program that you put in the cubic inch displacement the head casting numbers and valve sizes, intake year and part numbers, carburetor year and type, and cam, with the size of headers and exhaust, it would give you the HP and torque you could expect. It also made suggestions as to cam or valve sizes to get the best torque and HP at the speeds you wanted to run, and what you were doing with it. I keep hearing about exhaust, intakes and turbo's nowhere do I see anybody changing the cam. It all has to work together or it doesn't work properly, and the cam is the HEART of the whole thing. PLAY SAFE!