It can be done, I made one, I just have to remember how! I found a web site where a guy had made one, and it's basically some parts from radio shack. I think maybe 5 or 8 dollars worth. There was a potentiometer, a really small one that had like 16 turns from like 0 ohms to 10,000 ohms, or something like that. Basically, you splice into the 5 volt reference signal and it goes to the pot, and then splice into the return signal that goes to the computer, and from there, you can "bleed" in or "bleed" out extra signal to the computer. What you are doing in effect is moving the map curve up or down by a factor of "x" with the pot. I also put in a similar one to the temp sending unit. And to get it back to stock, I wired it to a three position toggle switch. This let me set it to normal, bypassing the pot I wired in, off, so basically the computer would not recieve any signal and would be in limp mode, running real crappy for anyone wanting to steal it, or position three which was with the pots wired in sending the "adjusted" signal to the computer.