SMA ON ILS APCH MAKES GAR DUE TO TFC AHEAD AND BELOW.

Narrative

WHILE INBOUND ON THE ILS APCH INSIDE THE OM; CHINO TWR; ACKNOWLEDGED OUR ACFT WHEN RPTED JUST AFTER PASSING THE OM. TWR FREQ WAS EXTREMELY CONGESTED AND NUMEROUS ACFT WERE IN THE PATTERN. I WAS WATCHING OUT FOR OTHER TFC WHEN I SAW AT 1 O'CLOCK LOW; A CESSNA 172 AHEAD AND BELOW US ABOUT A MI AHEAD OF US. I ADVISED THE PLT EXECUTING THE APCH TO LEVEL OFF AND PREPARE FOR A GAR SINCE WE HAD TFC BELOW US. I WAS NOT ABLE TO TALK TO THE TWR. MOMENTARILY DUE TO FREQ CONGESTION; BY THE TIME I INFORMED THE TWR; WE HAD PASSED TFC BELOW US AND WERE GOING AROUND. THE PLT OF C-172 SAID 'I WANT THE #'S ON THAT ACFT. HE MISSED US BY 25 FT' (THIS IS NOT TRUE FOR THE CLOSEST PROX BTWN THE ACFT WAS IN EXCESS OF 200 FT). WE CONTINUED ON THE GAR AND RE-ENTERED THE TFC PATTERN WITHOUT ANY FURTHER INCIDENT. UPON LNDG; MR X WALKED UP TO US AND SAID HE GOT SCARED WHEN HE SAW OUR SHADOW AND THOUGHT WE WERE TOO CLOSE TO THEM; HOWEVER I TOLD HIM HIS ACFT WAS IN PLAIN SIGHT AT ALL TIMES AND AT NO TIME WERE THEY IN DANGER OF A MIDAIR COLLISION. WE ALL EXCHANGED INFO ANDF DEPARTED.