I had this issue recently, I even ended up having a couple codes pop up and a CEL. I removed the chip, still had the issues, then I removed the harness and the issues went away. I just re-installed the chip Sunday evening. I used di - electric grease on all the connections like Quad reccomended, and it runs great now. My mileage is up slightly, and the extra power is nice. Man that thing does really mess with the overhead though. The last tank hand calc'ed to 17 mpg the over head read 21.4mpg. It is usually off by 2 mpg, now it is off by 4.5. Oh well.

 

Might be a dumb question- Should I run in the "stock" mode or level 1 or which for the best mileage? Is the stock setting actually stock or is it just stock horsepower with better fuel economy?

 

generaly with most boxes and programmers. . .the lowest setting is the mileage setting, and 0 being off.