[Aurel]

I`ve got this annoying little noise at mid throttle that is coming from the CIS area on the engine. I think sputtering is the correct term to describe it. It sounds like shaking a crankbait with a little bead inside, for those who fish...But this is not detonation, I run 93 octane, my advance is at factory specs and it definitely comes from the CIS/throttle area. I have also noticed my gas mileage has decreased, but power feels about the same. Something is going on in there. What could it be?
I adjutsed the valves and changed the oil last week-end, but I do not see how this could be related. Other difference would be that the weather is cooler now.
Any ideas?