AN MD80 NEARLY STALLED AT FL330 WHEN THE L THROTTLE WOULD NOT MAINTAIN THE COMMANDED EPR WITH ANTI-ICE ON. AN EMER WAS DECLARED IN CONJUNCTION WITH A DSCNT.

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ON FLT FROM ZZZ TO ZZZ1 ON 11/MON/05; WE EXPERIENCED LOW SPD BUFFET AT FL330. DURING THE INITIAL CLB; CTR TOLD US THAT WE HAD TO STOP OUR CLB AT FL320 BECAUSE OF COMPANY TFC AT OUR REQUESTED ALT OF FL330. THE CTR CTLR ASKED US TO CLB AT .72 MACH TO CREATE SPACING. ATC GAVE US A HDG TO FLY; AND SAID THAT WE WOULD BE CLRED DIRECT ZZZ VOR AT FL330 AND NORMAL SPD WHEN SPACING WAS ADEQUATE. FO WAS FLYING; SO I TOLD HIM THAT I WAS GOING TO MAKE A PA TO THE PAX. FO COMPLETED THE CLB TO FL330 AND THE TURN ON COURSE WHILE I MADE THE PA. SHORTLY AFTER LEVEL AT FL330; WE HAD A 'FORWARD CARGO DOOR' LIGHT ILLUMINATE ON THE ANNUNCIATOR PANEL. WE BOTH LOOKED UP THE PROC IN THE QRH AND WERE SATISFIED WITH CONTINUING THE FLT BECAUSE THE PRESSURIZATION WAS NORMAL. WHILE LEVEL AT FL330; WE ENCOUNTERED HIGH CLOUDS THAT REQUIRED ENG AND WING ANTI-ICE. DURING CLB; THE L THROTTLE WAS NOT KEEPING UP WITH THE DEMANDED EPR AND I MANUALLY ADJUSTED THE THROTTLE UP. WHILE IN CRUISE; THE L THROTTLE WAS LAGGING AGAIN AND HAD TO BE ADJUSTED FORWARD. WHILE I WAS ENTERING THE CARGO DOOR LIGHT PROBLEM INTO THE LOG BOOK AND ACARS; WE STARTED FEELING LIGHT ACFT BUFFETING. FO ASKED ME; 'DO YOU FEEL THAT?' I DID FEEL IT AND MY FIRST THOUGHT WAS MAYBE WE DID HAVE A CARGO DOOR PROBLEM AND I WAS LOOKING CLOSELY AT THE PRESSURIZATION GAUGE. THE BUFFETING INCREASED; AND THE FO ASKED ME; 'DO YOU WANT TO GO DOWN?' I DECLARED AN EMER WITH CTR AND WE STARTED A DSCNT. THE FO POINTED OUT THAT OUR AIRSPD WAS LOW. I PUSHED THE THROTTLES FORWARD AS HE DSNDED WITH THE AUTOPLT OFF AND WE LEVELED AT FL300 AND THE AIRSPD STARTED TO INCREASE. OUR WT AT THE TIME WAS 132000 LBS. SUPPLEMENTAL INFO FROM ACN 677228: WE HAD BEEN IN 'PRF CRZ' MODE WHILE LEVEL AT FL320. I AM REASONABLY CONFIDENT THAT WE WERE LEVEL AT FL330 IN 'ALT HLD' MODE WITH 'MACH SEL' AT .75 MACH WHEN THE CAPT FINISHED HIS PA. SHORTLY THEREAFTER; THE 'FWD CARGO DOOR' WARNING LIGHT ILLUMINATED. WE BOTH REFERENCED THE QRH PROCS AND DETERMINED THAT IT WAS SAFE TO CONTINUE THE FLT TO DEST. A SHORT TIME LATER; WE ENTERED A CLOUD LAYER AND SUBSEQUENTLY ACTIVATED ENG AND AIRFOIL ANTI-ICE SYSTEMS. DURING CRUISE; I HAD TO CONTINUALLY MAKE MANUAL ADJUSTMENTS TO THE THROTTLES TO MATCH INDICATED EPRS WITH ENG SYNCH SELECTED TO N1.