AO Platinum Member
Join Date: Feb 2002
Location: The land that Time forgot
It could be a loose manifold cover or some other resonance.
You can tell for sure by giving your boy a tankful of the highest octane rated fuel you can get your hands on (Super U/L @ 95 octane or Shell Optimax) or buy some proprietary octane booster and stick it in the tank.
If the noise goes away, then you should try shopping for petrol at a different garage. Supermarkets and some of the unbranded garages sell fuel that's down at the old 2-star rating (90 octane I think). Your Alfa needs 92 octane or above.
No bullets for Chaingun..