G'day Magista.
As RD says.
I'm assuming you have a concentric carb with the O ring. What size?
Your tufnol heat spacer should match the manifold hole and the carb.
Manifold, gasket, spacer, gasket, drip tray, O ring, carb.
With that miss match the intake will be subject to extra turbulence and restrict it.
Cheers