PLT OF A CPR PIPER MALIBU PA46 FAILED TO SIDESTEP TO THE OTHER PARALLEL RWY FOR LNDG AFTER ACCEPTING RWY WHEN ASKED BY TWR CTLR. HIS ACTION RESULTED IN CAUSING HIM TO EXECUTE A GAR DUE TO ANOTHER ACFT ON THE RWY FOR TKOF AND SUBSEQUENTLY TAKING EVASIVE ACTION TO AVOID A XTFC HELI. HE THEN CIRCLED DOWNWIND AND LANDED ON THE CORRECT RWY.

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APCHING PDK FROM THE NW; I WAS SEQUENCED #2 FOR RWY 20L TO FOLLOW A CITATION. I RPTED THE ARPT AND TFC IN SIGHT. APCH CTL CLRED ME FOR A VISUAL TO RWY 20L; CALL THE TWR. I SWITCHED TO TWR FREQ AND RPTED #2 FOR RWY 20L. TFC INTO PDK WAS EXTREMELY HVY. THE TWR FREQ WAS JAMMED WITH A NUMBER OF BLOCKED XMISSIONS. IN ADDITION TO THE FIXED WING TFC; THERE WERE SEVERAL TFC HELIS COMING AND GOING. A HELI PASSED BENEATH ME AS I WAS APPROX 1 MI OUT; BUT WAS NO FACTOR. TWR ADVISED A FALCON TO DEPART PRIOR TO MY ARR AND WOULD I BE ABLE TO ACCEPT RWY 20R. I ADVISED THAT I COULD ACCEPT RWY 20R BUT I DID NOT TAKE THIS AS A CLRNC TO LAND ON RWY 20R. I THOUGHT TWR CLRED ME TO LAND RWY 20L AND I THOUGHT I CONFIRMED CLRED RWY 20L. THE ENTIRE TIME I WAS ON THE ILS TO RWY 20L. AT APPROX 1/2 MI OUT; A PA31 PULLED INTO POS AND HOLD ON RWY 20L. I REALIZED THIS WOULD NOT WORK; SO I INITIATED A GAR; MAINTAINING RWY HDG. XING THE ARPT BOUNDARY; I SAW A JET RANGER XING MIDFIELD FROM E TO W. WE WERE ON AN APPROX COLLISION COURSE AND IT DID NOT APPEAR THAT THE HELI SAW ME. I TURNED R; AWAY FROM THE HELI. AS I WAS TURNING; THE TWR OPERATOR REALIZED WHAT WAS HAPPENING AND ASKED THE HELI IF HE HAD THE MALIBU TURNING TO HIS R FRONT IN SIGHT. I DO NOT RECALL HIS REPLY; IF I HEARD IT AT ALL. ALSO DUE TO COM SATURATION; I HAD BEEN UNABLE TO ADVISE THE TWR OF MY GAR. I CONTINUED MY R TURN AND MADE A NORMAL APCH TO RWY 20R. OBVIOUSLY THE TWR OPERATOR THOUGHT I WAS GOING TO SIDESTEP TO RWY 20R AND I THOUGHT I HAD BEEN CLRED TO LAND RWY 20L. ALTHOUGH THE TWR WAS DOING A TERRIFIC JOB SEQUENCING THE VOLUME OF TFC; SATURATION PREVENTED ADEQUATE COM. IN ADDITION TO THE HIGH VOLUME OF FIXED WING ACFT; THE HELI TFC FLYING THEIR OWN PATTERNS ADDED TO THE CONFUSION.