Why would the oil light come on when you are idiling and go off when rpms go up the oil level is ok is this due to a bad sending unit?

It can be a bad sending unit or it can be low oil pressure. Start by replacing the filter with a Motorcraft filter if you have a Ford or Purolator if you have a Dodge, and making sure you are using the recommended weight of oil. If the problem still exists then replace the sending unit.