runs rough and dies when idling
 

i have a 1991 Cadillac sedan deville it keeps dying when i let up off of the gas.... the previous owner had put regular fuel in the tank when it says premium only so I ran it dry and filled with premium and it got worse. its now dying randomly when i let off the gas as im driving i have to shift to N and quickly start it up again...

It also runs rough when idling like its about to die, sometimes it does.

when it dies the "change oil soon" and "charge" lights both come on....