One spark plug is too clean - modified exhaust tube time

Pulled the plugs on my 06 225 the other day and #3 was too clean for my liking.

Engine runs fine but does blow HO2 sensors on a regular basis. This engine has had the updated ECU and HO2 sensor fitted (as per SB 70 I think) so I thought that the modified idle exhaust tubes would have also been fitted, but seeing as this plug was seized in when I bought the engine - and the sensors keep dying - I'm now of the opinion that they haven't been changed.

So my job for the new year is to purchase and fit the modified tubes - I'm OK'ish at spannering and, having looked at SB 56, it seems it's merely a case of undoing a lot of bolts! Hope I'm right!

Suspect plug is at the bottom

Yep - I see what you mean. But it doesn't seem too bad. The fact that you are blowing HO2 sensors on a regular basis tells you it's time to change out those exhaust tubes.