The thing they are talking about is detonation. I highly doubt it is anything like that. First thing, inspect all of your intercooler hoses. Take them off, inspect them for cuts, cracks, or slits. Your engine has an AFM (Air Flow Meter). If the air that the AFM meters, does not enter the engine, the engine will run like dog shit. This means that when you take it to that RPM of 5k the IC hoses might be expanding and leaking the air. Sometimes this will cause the engine to shutter. I have experienced that personally. The sound that you are hearing, is it more of a click, or is it a knock? Knock is a pretty harsh term when it comes to engine noise. If it's a clicking sound you hear, you may want to check the exhaust manifold, you may have a leak there. From what you described, you may actually have a combination of the two.