FLC OF AN MLG FOLLOWED THE WRONG TFC WHEN CLRED FOR A VISUAL APCH DUE TO SIGHTING WHAT THEY THOUGHT WAS THEIR TFC. APCH CTLR INTERVENED AND PROVIDED TFC SEPARATION.

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WHEN WE WERE ON A R DOWNWIND FOR AN ILS RWY 27; ATC ASKED US IF WE SAW A KING AIR MANEUVERING FOR FINAL FOR THE SAME RWY. HE SAID THE TFC WAS AT 1 O'CLOCK POS. MY FO AND I BOTH SAW AN ACFT THAT WE THOUGHT WAS AT 1 O'CLOCK LOW POS AND WE CALLED THE TFC IN SIGHT. WE WERE CLRED THE VISUAL FOR RWY 27 BEHIND THE TFC. ON R BASE ABOUT 2.5 MI TO THE INBOUND COURSE; THE CTLR ASKED US AGAIN IF WE HAD THE ACFT TO FOLLOW. HE SAID IT APPEARED THAT WE WERE CUTTING INSIDE OF HIM. WE IMMEDIATELY LOOKED AHEAD AND TO THE L AND SAW THE ACFT THAT HE WAS TALKING ABOUT RIGHT IN FRONT OF US; ESTABLISHED ON FINAL. I TOOK THE ACFT OFF AUTOPLT AND BANKED L TO INCREASE SEPARATION; AND THEN MANEUVERED AROUND BEHIND THE TFC. THE ACFT WE HAD THOUGHT HE WAS TALKING ABOUT WAS ALREADY 3 MI OR SO UP AHEAD OF THE 'KING AIR' TFC (THE KING AIR TURNED OUT TO BE A BEECH 1900). THE REST OF THE APCH WAS UNEVENTFUL. I GUESS THE BEST WAY TO RESPOND TO AN ATC TFC QUERY WHEN HE WANTS YOU TO FOLLOW SOMEONE IS TO SAY SOMETHING LIKE 'I SEE TFC AT MY XX O'CLOCK POS AND ABOUT XX MI' AND MAKE YOUR VERY BEST POS ESTIMATE BACKING IT UP WITH TCASII INFO IF AVAILABLE. HOPEFULLY THEN IF THAT'S NOT THE RIGHT ACFT; ATC WILL CATCH IT. WE LOOKED AT THE TFC THAT WE SAW; LOOKED AT THE TCASII AND SIMPLY SAID 'ROGER; WE HAVE THE TFC' THEREBY DENYING ATC CORROBORATING EVIDENCE.