Just FYI there are a few things in the tune that are affected by not having a working VSS. They are:

1. Min N/V to Allow Fuel Shutoff - Minimum engine speed divided by vehicle speed in order for the engine to enter coasting fuel shutoff.

2. Min VS to Enter Coasting Fuel Shutoff

3. VS Below to Turn Fuel On - IF the vehicle speed goes below this value, the PCM turns the injectors back on.

4. Dashpot Min MPH - Stock setting is 5MPH

5. Dashpot Max Clip VS - Typically not used

6. High Speed Fan High Load VS to Turn On - Typically 40MPH. If you have a high load on the engine and are going over 40 MPH, then the fan will not turn on.

7. Low Speed Fan MPH to Turn Fan Back On - Typically 40MPH

8. Low Speed Fan MPH to Turn Fan Off - Typically 45MPH

9. Min Vehicle Speed for Open Loop Decel - Typically 20MPH

10. MPH for Open Loop Fuel - Typically 127.5MPH (Means your PCM will still try to keep the burn at stoich over 128MPH)

11. MPH to Return To Closed Loop - Typically 127.5MPH

12. Speed Limit values - There are 5 speed limit values in the tune

13. Vehicle Speed Sensor Switch - Can be used to turn off all the the VSS related stuff in the tune.

If you don't turn off the VSS in the tune, you may have a problem with fans staying on when they shouldn't (fan load and reliability issues?), coasting fuel shutoff and OL decel (fuel economy issues?), and dashpot settings (car may die on deceleration).