but on spark plug boss and lenght I don't. NA uses shorter plug because the pistons are not diched and there is not a lot of space between the piston and head. But on TT you have hemisferical dome with dished pistons. It will hurt performance the combustion will not be able to radiate on the piston compleately because at high rev there is no time. As for the boss its true it restricts air but thats very minimal. Nissan did that for reason.
The radiaton and combustion chamber pressures can not radiate downward in closed space. Pressure in closed room is iqual at all sides! Do you even know pascal's law of pressure?