Running fine-check engine light flashing-running fine again

I had an unusual experience today while driving my truck. My check engine light has come on a couple times recently (PO420) which refers to the catalytic efficiency system. Other than a little rough idle the truck had been running fine. I decided to add some Seafoam fuel system cleaner and do some aggressive driving.
I went out and drove about 15 miles and at times around 95 mph which of course is not how I normally drive. All of a sudden I noticed the truck was losing power and running rough. I looked down and saw the check engine flashing. I pulled over and turned the switch off. which is what you do when the check engine light starts flashing.
I started to call AAA roadside service but then decided to call one of my mechanic friends first. After sitting there a few minutes he told me to try to start it up. I did and there was no flashing or any other check engine light however it was still running rough. I revved it up and all of a sudden the engine started to run normal again. I then drove another 20 miles before going home and the truck is still running fine.
Has anyone else ever had this happen? Can anyone explain what caused this to happen? I will add my truck has 410,000 miles which is one reason I was using the Seafoam fuel system cleaner.

 

Flashing CEL usually means multiple misfires are detected, which can cause damage to the catalytic system. It flashes for just that reason, to get your attention to slow down and turn the engine off.

If I were you. I’d drive it “easy” until the Seafoam is gone from the tank.
Then run regular gas and see what happens. If you get the same CEL again, have it looked at by a professional.

 

So a flashing check engine light means you had a catalyst damaging misfire. So the fuel was being dumped into the cylinder not being burned and the ecu couldn't stop it. Raw fuel then enters the cat and overheats it. You already have worn out cats so its not a fire hazard but it needs to be addressed.

Typically I'm checking for fuel injectors leaking with a flashing engine light, I want to see why it was behaving as such. The seafoam may have trapped dirt and jammed an injector.

 

Look at the secondary ignition components