Increased Power and Performance: SCORCHER HD performance chips deliver significant power gains by increasing turbo boost as well as optimizing fuel injection timing and pulse width. Unlike many other chips on the market that flash IN the ECM, our performance chips receive data from the ECM and alter signals appropriately.Easy Installation: After removal of the vehicles ECM, the installation is a breeze. Remove the cover to find the ECM port connections, clean the ports, then simply slide the chip into the ECM. No cutting, splicing, or modifications of wiring is necessary.Four Power Settings: A knob can be mounted in the cabin for easy, on-the-fly adjustability to accommodate any driving situation. The four settings are: +50 Horsepower, +75 Horsepower, +100 Horsepower, HOT IN (up to +140 Horsepower)Fitment Note: This part number works with ECM DPC-402 code and supports the following box codes: FUT, GLF, HPA and XLE.This unit fits 1999 trucks built before 12/07/98; See 77-43034 for trucks built after that date.