Drop the bosch plugs in the trash can and go OEM AC-DELCO plugs that your book calls for.
Do not leave home without them.
They only hurt one time.
Also if it is hard to start after tune up.
Check your fuel pressure.
If it is not up to full pressure on a cold start the injectors will not squirt fuel.
If you run a K&N filter do not over oil it and make sure you keep the sensors cleaned like using electric cleaner on mass air flow sensor.
MT-2500