At this point the cause of surging could be :

1) fuel issue but yesterday i have checked filters pump all hose and carb , no restriction

2) fuel jet extension ?

3) fuel pressure is at 7 psi , is better at 9 psi ?

4) carburetor too small ? from calculator 572x7500 / 3456 would be 1250cfm , i have 1050 .. can cause this surging ???

4) rear tires unloading ? shock ? mmmmmm very strange

5) tight converter ? is 5000 RPM