| Message | in the least. There is a discrepency between the tach and speedo reading compared to the formula. I get about 168 MPH at 6400 RPM in 5th in a manual, using our formula. That's really only about 9% off and could be the result (as someone already stated) of a speedo in need of calibration, or the car could have smaller diameter tires. And the car can "theoretically" do those advertised top speeds, based on gear ratio, redline, and tire diameter. I don't know if I'd want to test a stock turboed Z in 5th gear at 180+ MPH , if for no other reason than it is under a great deal of load at 7,000 RPM, in 5th gear, and stock turbos. Just me. Take care, Mark 
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