Early Mugello 186s ran awful with filters IME. Especially if you messed with the exhaust and inlet timing.
Filters look gay. However, the top ring peg of my Racetour piston wore away to 0.5 mm and spun the ring after 3K miles. I'm wondering; crap fuel, road grit or poor engineering? I'm not sure, I'm still waiting for Mark to get back to me. But I know I'm not alone. Spooky.