Hc ppm
I would google vehicle exhaust gases & do some studying
Given it is a 1992-- 22 year old vehicle & don't know how old
the motor is !
159 is HC & a lot of unburnt fuel
NO may be an egr issue along with overheating
Best study the gases & what is required to address them
You could go with the spark plugs,wires,synthetic oil, new air filter,
check out the egr system,pcv system & vacuum leaks,thermostat,
oxygen sensor,clean maf sensor
I'm NOT saying throw parts at it,I'm saying check it out & do some
testing, to find some problems
You have to take out a lot of fuel & bring down your misfire counts,
engine temp etc
I would guess after your best efforts ,you need to replace the
exhaust converter,I would, unless it is only 5 years old or newer