How do I add a real flex fuel sensor to an E38 Camaro and dial in E85 — what needs adjusting beyond enabling multifuel?

Here is what the documentation says. Each point links to its source; tables and names vary by computer, operating system and tuning software.

• E38, E67, Terminator X, Dominator; LM7, LQ4, LQ9, LS1, LS3, LS6; 1999-2013: The flex fuel sensor is designed for installation in the fuel return line; its straight-through 3/8-inch (9.5 mm) tube adds minimal restriction, which suits high-horsepower fuel systems, and it resists the corrosive properties of high-ethanol blends. (Syvecs)
• E38, E67, P01, P59, Terminator X; LM7, LQ4, LQ9, LS1, LS3, LS6; 1999-2013: In observed real-world consumption, pure E85 raises fuel use by roughly 25-30% over gasoline (E50 only about 5-10%), and pump-labeled E85 can legally contain anywhere from 51% to 83% ethanol. (eFlexFuel)
• Sources differ: Conflicts with the 52% stoichiometric figure; the manual's observed consumption increase is smaller than the stoich-ratio math implies.
• E38, E67, P01, P59, Terminator X; LM7, LQ4, LQ9, LS1, LS3, LS6; 1999-2013: A proper E85 fuel system needs 30-40% more flow capacity than the gasoline equivalent; injectors should be sized to stay at or below 90% duty cycle and the pump should carry 10-20% headroom. Materials to avoid include PVC, nitrile, natural rubber, urethane, non-anodized aluminum, zinc, brass, and untreated ferrous metals, and pre-2001 OE fuel systems were not engineered for any ethanol concentration. (Performance Racing Industry)
• E38, E67, P59; LM7, LQ4, LQ9, LS1, LS3, LS6; 1999-2013: Advanced Fuel Dynamics' E85 system uses the GM-style inline sensor to monitor ethanol content and automatically steps injector output up as ethanol rises; the sensor re-reads content every 1/10 of a second, so blends adjust on the fly without a retune. Pump E85 can range from 51% to 83% ethanol. (MotorTrend)
• E38, E67, P59, Terminator X; LM7, LQ4, LQ9, LS1, LS3, LS6; 1999-2013: The GM/Continental flex fuel sensor uses a three-wire connector: ground, battery-positive power, and a signal wire carrying ethanol percentage as a frequency signal. The ECM supplies an internal 5V pull-up on the signal circuit, which the sensor pulses to ground; normal operation is 50-150 Hz, while 180-190 Hz flags contaminated fuel. (CPR Racing)

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