Advice Needed! P0401, P0300, P0301, P0303 Head Gasket and/or EGR?

Yes! Somehow I took the picture (or uploaded the picture) upside down

“AFAIK NGK were never the stock-from-factory plug. Previous owner replaced, possibly counterfeits?”

Actually, it was me. I just replaced the spark plugs around 3 weeks ago with a set I bought online. Now that I think about it I wonder if they were not gapped properly and also not torqued properly (cylinders 1 & 3 were very loose) Could also be a counterfeit issue for sure.

"I’d still be on alert regarding the head gasket.”

Absolutely. Cleaning the EGR asap, purchasing the oil catcher and procuring a borescope and gas test kit. Any other suggestions on how to proactively monitor the head gasket @Mendel Leisk?
Thanks again for taking the time to help me, I sincerely appreciate it!

 

That's a revelation lol. Was that just before the symptoms/codes started? The plugs could well be the cause of the shake-on-startup. I would take it as wake-up call. Your EGR will be clogged, guaranteed with the miles, and head gaskets have blown well before those miles. Just keep an eye on the coolant level, get on that EGR cleaning as soon as you can manage.

For sure get a set of Denso's, preferably from dealership; latest has the number 16 instead of 20.[/QUOTE]

That's a revelation lol.
Sorry about disclosing the new spark plugs so late/vaguely, I mentioned it on post #5 as an edit note.

Was that just before the symptoms/codes started?
Yes, the spark plugs were replaced around 3 weeks ago (two weeks before the trip), no issues whatsoever before or right after installing the spark plugs 3 weeks ago. The car never shook or showed any other malfunction signs at all at start up or at any other point. Actually, no issues whatsoever until after the temperature warning light and CEL came on last week after going 75mph uphill during our camping trip. Definitely a wake up call.

Do you think the subpar (to say the least) spark plugs were ok for a while (3 weeks before the trip) for city driving but failed when put under stress (high speed going uphill with ac on full blast)?

Or do you think the clogged EGR caused the spark plugs to fail? (if that was the case, wouldn't the car shaking on start/idle before the trip and even now with the new spark plugs)?

I was just going to ask about the 16 and 20 you mentioned on your previous post, thank you for clarifying!

Is there a particular oil catch can that you recommend?

Thank you again for all your help!