Struggles after 4900 rpm

If you take the spark plugs out and have a good look at the white ceramic there shouldn't be any black or metallic speckles on it. If there are very tiny spots of metal looking dots on the ceramic then you've had detonation/pinging and the small specs you are seeing are molten bits of metal/aluminum from your combustion chamber.

Don't worry though I don't think this is your issue. Try changing things back one at a time and see if you find your culprit. Another problem might be the ignition box (module) breaking up at higher RPM.

Burntorange70 had a great point. I'm actually having an issue with my car now that its really hot here in Toronto. It could very well be a fuel delivery problem where the fuel is boiling in the fuel line and the pump can't deliver enough fuel to keep the bowls full on hard full-throttle runs. Have you tried driving it when it is cool out (evening) to see if the problem is the same?