CGA ACFT ON APCH TO TEB HAS AN NMAC WITH AN UNKNOWN TWIN ENG ACFT. TFC NOT ISSUED.

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DURING DSCNT; WE WERE TOLD TO EXPECT THE TETERBORO VOR- DME APCH; ALL WAS PROCEEDING NORMALLY ON THE ARR (STAR) WE HAD BEEN ASSIGNED. APCH CTL CLRED US FOR THE VOR-DME APCH; 'MAINTAIN 3000 FT TO WANES INTXN.' APPROX 1/2 MI W OF WANES; WE IDENTED 3 TARGETS; 12 O'CLOCK POS; SAME ALT; ON OUR TCASII; LESS THAN 5 NM AND CLOSING. THE CAPT CHOSE TO DSND MOMENTARILY TO AVOID COLLISION WITH THESE (PRESUMABLY) NO XPONDER (AND SCUD RUNNING) ACFT THAT APCH WAS NOT AWARE OF. WE DSNDED AS LOW AS 2300 FT FOR A MIN OR SO IN ORDER TO AVOID COLLISION; AND AT THE LAST MIN; DIRECTLY OVER WANES SAW A TWIN ENG ACFT EMERGE FROM CLOUDS AT OUR PREVIOUS ALT OF 3000 FT MSL. WE IMMEDIATELY INFORMED THE NEXT CTLR WE WERE 'LEVELING' AT 3000 FT;' AS ASSIGNED FOR THE APCH; AND THE REMAINDER OF THE FLT WAS UNEVENTFUL. THE CAPT AND I DISCUSSED THE SIT AND FELT THE CTLR MUST HAVE BEEN OVERLOADED TO HAVE NOT BEEN ABLE TO ADVISE US OF THE 3 TARGETS AT OUR ALT; ON A COLLISION COURSE DIRECTLY TOWARDS US; AS WE WERE UNDER POSITIVE CTL FOR THE IFR APCH TO TETERBORO; AT THE ASSIGNED ALT. I FEEL THAT IN THIS DENSE TFC AREA IT WOULD OF COURSE HAVE BEEN BETTER TO TELL THE CTLR OF OUR ACTIONS EARLIER; BUT DUE TO INTENSE FREQ CONGESTION; WE JUST COULDN'T 'GET A WORD IN EDGEWISE.' BECAUSE OF THIS AND OTHER TCASII 'SAVES;' WE BELIEVE STRONGLY IN OUR EQUIP AND WISH CTLRS HAD SOME IDEA OF WHAT OUR JOB IS OFTEN LIKE IN BUSY ARPT ENVIRONMENTS LIKE THIS. I WOULD BE HAPPY TO ELABORATE ON THE PROBS OF TETERBORO; AS IT REMAINS ONE OF THE FEW ARPTS WE FLY INTO THAT SEEMS TO ALWAYS MAKE FLCS A BIT MORE ANXIOUS AND THEREFORE VERY VIGILANT.