Spark knock?

Over the last two trips to the drag strip, I’ve been noticing an issue with the motor on the top end – i.e. between 5K and 6K RPMS. It sounds like a popping or crackling noise which I can’t figure out. My initial thought was that it may be the alternator or one of the other bearings on the pulley system. My other thought was maybe it was a slight exhaust leak coming from the header to midpipe connection. Somebody on the other forums suggested that it might be spark knock, which I think may be the problem.

I’m running a stock 2V 4.6L setup with catless h-pipe and an SCT 93 tune and some octane boost. Last summer, I changed out the spark plugs and bought a set of used coils on eBay to replace the stock ones for really cheap. I did this as a preventative measure really. However if the problem is spark knock at high rpms, my first thought would be a bad coil or some fault in the ignition system.

So my question is this: what is spark knock and how do I identify it? Is there a way to test each of the coils for functionality? I have read tons of threads about keeping the stock coils because they work just as good as the MSD or Accel aftermarket ones. I don’t have an A/F gauge but I’m thinking of pulling the plugs just to see if any combustion problems exist. Is it possible I have a bad coil then? Thanks for your help guys.

Okay yah ill try adding fuel and see what happens then. This may be a dumb question, but how do you pull timing? I see I have a timing adjustment on the tuner, should I retard timing until the spark knock goes away? I'm really green when it comes to tuning so any help I can get would be tremendous.