Arduino IDE (Integrated Developer Environment)

The IDE allows you to write and customize speeduino code, you don't need to do that, but you do need the IDE in order to upload existing code made by others into your ARDUINO device, so you need this to upload code to the ARDUSTIM and the SPEEDUINO devices.
You do NOT need this IDE to upload ENGINE TUNES to existing devices, that is done via Tuner Studio a commercial product.

Arduino IDE