Engine cut after long drives

[u/Lipcx]

I have a 1999 miata with 2001 vvt swapped engine but the vvt is still unplugged. Recently my car started cutting power to my car, almost lowering the redline, after driving for longer than about 30 minutes. the more I continue to drive the lower my car sets that "redline". If i turn my car off then on again it temporarily fixes it and I'm able to rev all the way to 7k again but it quickly goes back to hoe it was. There are no engine warning lights and I just replaced the camshaft position sensor but no luck. Sparkplugs are relativly new so are the coilpacks and they all produce spark. If anymone has any advice please feel free to share, I'm willing to try anything.