Originally Posted by iNVAR
It is impossible, without physical modification of the car, to make the turbo generate 0% boost under throttle at that speed because the load on the engine is high enough to cause the turbo to generate boost. And because it's a feedback system, it's not possible to open the wastegate to bypass the turbine until you're generating the required wastegate boost. Get it?
^This. OP what you are asking for is impossible to accomplish with a simple tuning re-program. To do what you want would require a physical modification of your waste gate as well as a custom tune. Even then I don't think you will realize better fuel economy trying to keep your car moving at 80 MPH with no boost.