P0301 Code + oil high/smeared on 1 side of dipstick??

Butttt, you could have a failing head gasket also...

 

The spec'd plugs for gen 3, from my notes:

spark plug: denso SC20HR11 (per Owner's Manual (toyota p/n: 90919-01253)<superceded by Denso SC16HR11 (hotter plug, revision by Toyota)

I'd concur about the head gasket, gen 3, over 200k miles, code P0301, almost undoubtedly head gasket failure.

 

I didn't say it WAS a head gasket..... It's possible.
Has your coolant level gone down?
Misfires and low coolant is a strong indication the head gasket has failed.

It is possible it's just the bad spark plugs....
Replace them with good ones, and if the misfires go away, you've found the issue.

 

Not "definitive", but you've got a gen 3, it's got 206k miles, it's showing P0301, and you're getting shakes.

Has the EGR ever been cleaned?

 

Replace the plugs, clear the code, and go from there. It wouldn't hurt to look in the cylinders while you have the plugs out, but there's no reason to be trying to diagnose something else when you have spark plugs that look like that.

(that being said, at 200k your head gasket is a ticking time bomb)

 

Bad plugs or coils will cause misfires all the time and not clear up after a startup rattle.

It takes a series of misfires to set the code; most with early hg symptoms don't get a code and see no coolant change due to the small quantity of drops leaking into the cylinder for a short time.

Wait long enough and it will rattle with an engine start after a stop light. Now you are risking a stranding when you blow a hole in the block. Then its replacement engine for sure and the options go from bad to expensive (used salvage yard, JDM used in Japan, Pro rebuilt with new pistons and rings).

Dual view borescope on a cold engine with coolant pressurized can be definitive as can viewing steam cleaned piston(s).

 

Shortcuting cost like the Prius also eh? Counterfeit plugs everywhere.

Real authentic plugs that will cost $20 more can go 120,000 and look a lot cleaner than your plugs. Sorry to pee in your Cheerios as a member here used to say.