didnt pass smog, need help!!!

[ureact2]

Well first of all, idk if im posting this in the right place or not. Im fairly new to here.
I live in california and well smog is strict up the ass here so my 92 coupe didnt pass star smog so i can register it under my name. i just bought the car off some dude. The car runs stronger than pop eye after he eats his spinach. I passed everything but emissions on both 15 & 25 mph failed. After the smog, i checked the spark plugs and noticed that they were burned so i changed them. I Changed the oil, oil filter, and air filter too and i added that stuff you put in the gas tank to remove gunk in the engine. Ever since i bought it off the guy, i put 91 from the shell gas station. I havent resmogged it because i think imma fail and im not tryna waste money. I have a generic exhaust but i dont see any type of smoke come out of it unless once it starts. My brothers g37 sedan does that smoke when it starts too but idk if that affects anything. His passes smog, btw lol. So should i take it back to resmog and hope for the better or could it be something else wrong on the car? Its a stock ka24de btw

NO (PPM)
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MAX | AVE | MEAS
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15mph: 559 | 242 | 1459 FAIL
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25mph: 516 | 179 | 254 FAIL

[dorkidori_s13]

change the 02 sensor, check for vacuum leaks around the motor, buy a new cat (never hurts, but youre in cali so it may hurt quite a bit), make sure timing is right

as far as EGR service is concerned, ill let someone else fit that advice as ive never dealt with smogging a KA really. im sure there are other things members will suggest as well.