Seems I got the p0300 misfire blues.

The engine runs smooth and isn't noticeably misfiring and runs like normal. It seems to make the code happen within 5 mins of starting the car and if I clear the code it doesn't come back till its cold again.

The engine pulls good vacuum, and I just replaced the cat and plugs earlier this year.

I have no clue as to what could be causing these issues. My only though could be dirty injectors or something?

Any direction would be cool.

Not sure if its related but I usually get a p0455 code as well.....

What plugs did you put in?
The 455 code is probably the evap vent valve

Ive had the 455 for quite some time....really doesnt concern me unless it could be causing an issue.

Plugs are NGK 3787's

I changed the plugs and it didnt change anything...I was on NGK 9509's before. It started when I was on those. The 3787's are the exact same but have a smaller pre gap.

im gonna share what was shared with me. i was told the best thing to do is stay away from other brands of spark plugs and stick with delco plugs. some plugs dont react the same with gm engines as with other engines. and if you still havent figured out your missfire check your coil tower housing. ive gone through three and its fixed my problem everytime. the last one i just had replaced which was earlier last week the tech that was working on my car told me he never wants to work on my car again cuz that was the only thing he didnt check since it had been replaced two months prior

Thanks for the advice....

My car is far from stock. NGK is who makes AC delco plugs so the plugs are not the issue. Ive swapped coil packs and icm's. The problem isnt really around much anymore (knock on wood) Ill get the odd code set but im thinking its to do with a lazy lash adjuster I have. Not to worried.