No more than a couple months ago I switched my plugs to Bosch +4 , the previous owner had already put in STI wires and (unknown to me) Bosch +2 plugs. About a month before changing the plugs I ran a can of seafoam through the tank and one through the intake.

So what I'm wondering now is: where did the damn piece of carbon come from? Could it build up on the spark plug over a couple months or did it come from somewhere else? Anything I can/should do about it? Should I run some Seafoam again or BG44K?

Other than this the engine runs fine, temps constantly in the low 200s around the city, low 190s on the highway...

Thanks for any opinions.

 

IMHO no need to run cleaner again. Might want to consider the 180F soft spring thermostat, but your temps sound better than many. But it gets warm inside the Beltway (all the politicians talking at once and doing.... well frankly not very much).

 

Thanks, I know about the 180 Thermostat, I'll change it in the spring when I plan to put in new coolant hoses.

I checked my air filter today and it looked a bit tired so I decided to put a new one in. I noticed some junk in the bottom of the airbox but the top part was very clean. Still wondering how the plug got fouled so quickly with carbon..