here is how to down grade the unit if you F up your upgrade or have missing info from your upgrade insert your disc in to your unit then go to settings tab find the menu that lets you change the language change the language to either french or spanish let let the dvd upgrade the unit after its done do it all over this time change the language back to english hit the eject button and insert your old 70's disc let it upgrade / downgrade to english or do what I did give Pioneer 120 bucks and upgrade to the 90's disk

 

Most of the torrents are crap any way and the dude In Flordia ( same guy on Ebay ) his discs are not complete

 

 

I used this when I bought the fake discs and found out they don't have all the info on them

my N4 came with the cndv-70mt disc I tryed to upgrade to the cndv-90mt (fake dvd) it worked ok but it was missing map area's weeks later I got a message please insert app disc needless to say I was pissed I found this tip online some were and thought that other might need it sorry if this is a over post but if it helps some one then its the info they need