[abig84]

I always thought it was from having a lean condition? My obs with a tbi 305 used to do the same thing and the exhaust always smelled lean and so did the plugs but ran great so I never wanted to mess with it. Premium fuel did fix my issue but got expensive so I did it every other full up.

Unfortunately I don't know a fix as it magically fixed itself after like 4 years of doing it you can google premature detention and read up on some articles