A/C PARTS DOES IT MATTER WHERE YOU BUY THE FROM? I WAS THE RADIO ABOUT THIS

I'VE BEEN AN AC TECH. INDEPENDENTLY 12 YEARS NOW. AND JUST CANT FIGURE OUT WHY MY AC IS NOT COLD ENOUGH!
RADIO GUY SAID I NEED QUALITY PARTS, HE ALSO MENTIONED EVEN THOUGH I REPLACED THE CONDENSER A COUPLE TIMES DOESN'T MEAN ITS GOOD. THAT'S THE THOUGHT THAT KEEPS GOING THROUGH MY HEAD, CONDENSER IS JUST TOO THIN. 4 LBS OF FREON AND A LITTLE THIN CONDENSER JUST CANT COOL FAST ENOUGH! I DONT MAKE PARTS I JUST INSTALL,
NEWER CARS HAVE VERY SMALL CONDENSER PORTS AND NOW DAYS ONLY TAKE ABOUT 14 OZ OF FREON. SO THERES USUALLY NO PROBLEMS THERE.
I BELIEVE I JUST NEED OEM PARTS FOR THIS TRUCK...