All you could want to know:
TTS - MasterTune EFI Programming Software
The Master Tuner is made by The Turbo Shop (TTS). They made the original Screamin Eagle Race Tuner (SERT) and sold them under contract to Harley-Davidson. They had a "disagreement" and Harley-Davidson pulled their buisness and went to Kent-Moore to make the new Screamin Eagle Professional Super Tuner (SEPST).
Meanwhile, TTS went ahead with their knowledge of the Delphi EFI system and produce the Master Tuner.
The master tuner has a bunch of nice features that the SERT didn't have and the SEPST still doesn't have. They allow you to compensate the Speed Sensor pulse to accommodate any pulley changes or wheel changes. They have a bunch of tables that were originally hidden, opened up for you to be able to manipulate. Most significantly, you can use the V-Tune software to create a VE table using the stock narrow band switching sensors on any HD that has the closed loop EFI.
Can you tell which I think is better?
