Cadillac Repair: 1992 CADILLAC DEVILLE 4.9 MISS/TPS, rotor coil, cylinder problem

Question
1992 DEVILLE 4.9, PURCHASED CAR, HAD BAD MISS, NO CODES, NO ENGINE LIGHTS, DROVE 70 MILES HOME, 1/2 WAY HOME CLEARED UP, NO MISS, PERFECT, SHUT OFF, THEN RESTART AND HAD ROUGH MISS/IDLE AGAIN, CHANGED CAP, ROTOR, COIL, CHECKED WIRES, STILL BAD MISS, MEANWHILE POWER WASHED ENGINE, AFTER THAT, ENGINE LIGHT CAME ON WITH TPS SHORT, CAR WOULDN'T START UNLESS 1/4 PEDAL WAS DEPRESSED, GAVE CODES 21 AND 26, I BOUGHT A NEW TPS, ITS HARD TO ADJUST SCREWS WITHOUT REMOVING THROTTLE BODY, SO I PUT IT ON AS CLOSE AS THE OLD ONE,, WAS CAR THEN RESTARTED, BUT STILL HAS THE MISS....?? ANY HELP I WOULD MUCH APPRECIATE

Answer
With the engine running, start pulling spark plugs one at a time and see which spark plug does NOT make the engine run worse than it already does. When you find the spark plug that does not make the engine run worse than it does now, You found your cylinder problem.