[Darryl Ramm]

So you need to keep doing detective work. So put all the plugins back and go searching for denormalization problems. or put plugins files back in groups, maybe by AAX or RTAS by vendor and see when it starts misbehaving. It may not be a single plugin, it might be multiple ones. But plugins are still the best explanation on why a more powerful system will see more load.

My suspicion is you still have plugin misbehavior, maybe denormalization causing otherwise well behaved plugins to start consuming lots of CPU.

If you have disabled hyperthreading then set #CPU to 7 on an 8 core processor... that leaves a core for the operating system. And losing hyperthreading usually does not reduce real available compute power.