Misfires and does not start, now

Yes, there is a possibility the plugs could be causing the problem. Check the spark plugs ,One at a Time, to see what the electrode end inside the engine looks like. It would be a good idea to change them anyway. There are other reasons for a misfire. I have attached a link giving a list of other causes of misfires.
https://www.arnoldclark.com/newsroom/2502-the-most-common-causes-of-engine-misfires

there is something wrong in your transmission or differential, kindly check it

G16 misfires there are over 50 causes,
do you have tools? and gauges, and meters?
overheated before, so not now right?
new engine, so compression over 170psi, ? at sealevel?
seems its not in USA< right>? (if not , the many parts are different that is why I ask country)
our 95s are called sidekicks and trackers.
im guessing you are in canada posting to a USA forum?
jerking and cutting out. when?
hot engine cold engine, or both????
idling in park (is it AT? trans?)
idling in drive.? misfires,. at all times.
driving in gear,? only.
cruising, only misfire?
does it misfire, accelerating or wide open throttle. only?
only up hills , only in some gears?, only in turns,
ECU operates in many modes, (as above) and these facts aid diagnosis big time.
or is jerking and cutting out not the engine, but the 4 speed trans doing that. as any AT sure can do. (gear, flare ,gear ,repeats)

27 reason just here.
http://www.fixkick.com/misfiring.html

my guess, is battery is 13.3 to 15vdc running.
that it's bad spark got new cap,rotor wires and spark plugs.?
old 21 year factory HV wires are helpless, get some BOSCH mag wires, on this G16, best there is for this weak spark engine.

did you gap the stock class plugs at .028" or leave them at NGK .045"
which is wrong, dead wrong. are the plugs OEM plugs stated in the NGK catalog, free to read online? or what ever brand you use?
Did you time the cam right.? not using the false markes on cam cog?
did you then after that, time the distributor to 5deg. btdc or as your book states? using the timing freeze jumper and the timing light?
some are 5deg others are 8. degrees. depends on state or country.
if i knew all ways it misfires, id be more savvy but dont.
good luck..
PS:
id pull all 4 sparks out.
1: color, is tan? ok,.
2: coal black.?
3: black oil soaked.?
4: fuel soaked. even dripping , injector stuck open. on 1?
5: green antifreeze soaked.
6: damaged.
1 bad or all 4 or what, this is called READing the spark tips
and is a HUGE CLUE.

one if the reasons for misfires is low fuel pressure/ pump
when loaded there is a requirement for more fuel and if the pressure is too low then misfiring occurs
if it doesn't happen when the tank is full then that will be a reasonable expalnation

but does the fast right foot save the stall.
cut out has 2 meanings.
misfires. or stalls.
use those 2 words and all is 100x better.
and for sure misfires do cause stalls.
as does 50 more reasons.
wana guess or test?

You change the Front or Upstream Oxygen Sensors
every 100,000 miles or sooner, if they fail or slow down,
on ALL Vehicles

The Rear Sensors can stay until they fail

Doubt the Cylinder Misfires are from the O2 Sensors

You have to look at the reason for & correct the misfires

You should have a steady or flashing dash light on

If so, stop using it before you ruin the converter & get
it diagnosed & ALL Vehicle problems resolved at one time

try 0 timing carbon in your pistons can create similar problems,special wen engine is hot.

You may have 1 bad coil not both #3 & & #7

You also have a bad exhaust converter from 10
years of on & off misfires

The PO420 is (Bank 1) Passenger side

Fix the misfires

Replace both Converters

Replace all 4 O2 Sensors

Converters should have lasted a few more years

A cop ignition coil is $59.00 & takes about 15 min to put in

No reason to pay someone $500.00

coil packs are likely. . also moisture in the distributer cap. as well as injector problems, 1 bad injector will cause multiple misfires

wiring worn