they do and i am…but liek i said…i say it and was just wondering…wasnt plannnig on getting it
This is just a shitty version of a good idea. Jacobs electronics has been selling a unit to stabilize voltage in automotive electronics for a while now. You can’t just hook up a condenser to stabilize the voltage. It’s only going to come into play under high amperage demand, which your sensors and ignition system are not. The input voltages are important to the engine electronics. However your going to need a unit which has the ability to both increase and decrease the voltage to keep the inputs steady. Check this unit out. http://www.jacobselectronics.com/ProductDetails.aspx?brandId=13&productID=3681957&majID=525&minID=5293&selection=0&minselection=6
this is really interetsing me now. i know on the ebay ones they had a dyno graph for a porshe that gained 23hp from the stabalizer and i thought that was too good to be true
Case, and point. If it really worked why don’t manufacturers do it. 
Because manufacturers aren’t trying to squeeze every last drop out of your engine. Turbos work really well but you don’t see manufacturers put them on every car they produce. There is no added value for a manufacturer to add this to a stock vehicle.