Methods and systems are provided for reducing variability in air-fuel control due to variations in brake booster vacuum levels at an engine start. In one embodiment, the parallel processing system includes an instrument interface parallel controller to control a tray motor driving system, a close-loop heater control and detection system, a magnetic particle transfer system, a reagent release system, a reagent pre-mix pumping system and a wash buffer pumping system. The first resistance layer is formed from conductive polymers. Alternatively, the dosage form is about 15 mg of hydrocodone and about 500 mg of acetaminophen taken twice daily.