Failed emissions....high nox

First I recommend changing spark plugs, air filter, and change the oil & filter. If these are dirty or fouled up it will kill your millage and help to fail smog.
You can reduce both NOX and CO emmissions by adding denatured alcohol to the gas tank. Run it down to a bit under 1/4 tank and add 1 1/2 gallons. It makes the engine run a bit rough, but really clean.
If you still fgail SMOG then you need a new catalytic converter.
I used to "trick" my 86' with alcohol, but just rebuilt the engine so I put a new Cat on it. It passed emissions with WELL BELLOW numbers.

Good luck.

wow, no context but i can read your mind?
ok SMOG failed. right?
what speed, there are 2 in uSA, 15 and 25.mph.
so there are 3 tests, which one. all are PPM in usa.
parts per million.
but is that HC , CO, or NOX? or ?

based on your numbers is HC
hydrocarbons or in barstool, its raw gasoline leaving rear of car.
unburned fuel..

572 ppm is way too high 12-19 is normal
id say the CAT is bad.
but can be , engine is bad, and burned out the cat.
that is why all savvy mechanics, check the that the engines
holds closed loop status, (EFI closed loop) at the speed yours failed.
if not in closed loop the cat will burn up (rich)
that is first.
Once that is cured. you check HC again. if out of spec
you did burn up the can , new cat time.

that is the correct way.

get your injectors cleaned. change the air filter .change your plugs. put a fuel cleaner in your fuel tank.

Sounds like you lost O2 Control

Check fuel trim & data with professional
scanner & such

You done as far as working at home, you did all
you can

You have a rich condition (CO)

Seems as though the coolant sensor is not working &
your in open loop

fist i would like you to post the year make and model of the truck along with the HC ppms and NOX ppm it would be very helpful but high hc and nox can be attributed to a faulty EGR system nox is produced when the combustion chamber temperature gets too high so a small amount of exhaust is cycled back into the air stream to help cool them there are other causes but without looking at the levels its much harder to say

1) please RUN the scanner and computer test from any repair shop you must get the exactly faulty in your emission system
2) However you can go to the www.automecanico.com+ www.autoelectronico.com this sites is in spanish, but you can translate with your web browser and I Higly recomend because has Powerful information update for any cars models, Try it and fix it.
God bless you

HC is hydrocarbons or unburnt fuel.(raw fuel ).NO no such gas measurement.did you mean CO this is carbon monoxide or incomplete combustion.(all the fuel is not being burnt).if you mean NOX this is nitrates of oxide and is related to a heat problem.(motor running hot,bad catalytic converter).its probably getting too much fuel and not burning it all,possibly tune-up problem,carburetor(if it has one),bad fuel injection system(dirty injectors),computer(if it has one)may be getting a wrong signal.these are in reference of high HC and CO.for high NOX cooling system not keeping motor cool enough,cooling fan problem(weather clutch fan or electrically controlled cooling fan),poor cooling system circulation,bad catalytic converter.not a running lean problem as the other gases indicate rich problem.the converter may not be able to convert the emission gases to H2O and CO2 out the tailpipe.

Borrow or change the MAF completely,you have a LEAN combustion condition.The MAF could very well be the problem as it is the most common source lean combustion.
You will need a catalytic converter in good shape.

Change the lambda/oxygen sensor in the exhaust.