you cannie defy the laws of physics captain.
Don't do it
Don't even think of doing it
You obviously don't have a clue
Darwin awards will be contacting you :D
The cartridge probably will only require cleaning. However I've once removed the flow restrictor as this was making the boiler squeal like crazy. You may also have a partial blocked plate heat exchanger too. Your gas safe guy shouldn't need to remove the gas valve to access it tho. The pumps...
I'd be checking the inlet cold water filter first. It's a cartridge directly below the hall effect sensor. Housed inside the hydraulic inlet assembly. That's the brass part behind the pump. It also has a flow restrictor inside. I'd guess that's where the squeal is coming from. The next place may...