Dealer can't help so I turn to the experts....... Strange noise coming from engine at 3400 rpm. It stops about 3600 rpm. I 've never heard 4 cylinder detonation to know what it sounds like only V-8's. I put some octane booster in to see if it would stop. Waste of $6.00. It does it at all throttle positions, when hot, when cold, etc. I have a 2003 Type-S with AEM cold air, Greddy Evo exhaust and a Hondata reflash. Anyone have any ideas. IT'S DRIVING ME CRAZY!!!!!