Well because the owner did not properly maintain their cooling system they probably have alot of rust and corrosion causing the intake to seize to the block. Soak the Intake as well as possible with PB blaster overnight. Take a 2X4 and put on the flat of the lower intake. Take a large hammer and whack the 2X4 being careful not to miss and cause any damage to any other component. Repeat until she comes free.