I have a 1999 9-5lpt with 180K on it and it has been having some issues since the reacent transmission swap. The car has started to not keep a constant rpm beteen 2500 and 3000rpms above and below that it is ok. Both the tack and turbo gague are jumping rapidly up and down. The idle also dose a quick drop of and pick back up when i come to a stop. does any one have a thought as to what might be causing this?