I've had the 600 HP naturally aspirated one since before the Holley Sniper system came out... I run a Tanks Inc fuel tank, full return system, No real issues with the install, I did have an issue with the first unit, around town & driving in the mountains it was great, but if you got rolling down the highway in a steady cruise for an hour or so it would forget how to do anything but steady cruise... Accelerate & it would go lean, decelerate & it would load up.... Took me having a friend drive for a good hour steady while I viewed parameters to realize the Map sensor output would freeze.... The map sensor is built into the main body & not serviced separately.... FiTech replaced the unit no questions/no hassles.. The new unit has been flawless for about 8,000 miles so far...