Here's an interesting post from Julian at autospeed.
I would like to give it a shot in my TDI, but I'm not too sure how to go about it.
When messing with the MAP for more boost, some people add a diode to reduce the 0-5v MAP signal voltage, so the ECU thinks there is less boost and calls for more. Others replace the stock 2.5 bar MAP with a 3 bar to achieve similar results.
So I'm looking to do the opposite. I could replace my 2.5 bar MAP with a 2 bar MAP, but then I would have less boost even when I need it. I could add a second stock MAP just at the turbo's outlet and switch the input with a switch as suggested in the article, but that would cost me a 70 bucks MAP.
An other way, and potentially cheaper, would be the opposite of the diode on the signal wire mod. How would I go about building something simple and cheap that at the flip of a switch adds a fixed amount of voltage to the signal? Say I want to add 0.2V to the 0-5V signal?