You're breaking it

I'm having it rebuilt the way the engineers designed it. Opel/Vauxhall/GM crippled it by having narrow air tubes and narrow exhaust...

and they restricted the fuel inlet, and the pressue inside each of the 4 cylinders

so that they could reduce its power. With a weaker engine they could use cheaper components (gearbox, etc) that can't handle much power.

So you're buying a bigger gearbox as well?

nah... the current one's to handle a constant rate of 230Nm torque. On full throttle, the engine pushes an average of 180Nm to the wheels.

... peaking at 200Nm

We'll see