EFI Tech: GM Gen III 2-Bar SD Conversion Converting the GM Gen III LS engine controller to a custom 2-bar Speed Density OS allows you to go big on boost on your modified LSx engine. The 5-minute video below shows you how to complete the conversion quickly and easily. If you’d like to learn how to tune and calibrate EFI engines, click here and check out the best book ever written on the topic. Master EFI Tuner by Dan Maslic has sold thousands of copies in 38 countries world-wide and is used by many technical schools and colleges as THE textbook when teaching students about EFI, tuning and calibration. Click here to learn more about the book or to order your copy today!