[DukeDesmo]

It might depend on which region in Italy you are from, many dialects.

For instance, i had always assumed it might "tight head", however a good buddy of mine confirms the "narrow"

As an Italian speaker I can confirm;

Testa = Head

Stretta = Narrow (or tight)

Stretta is actually the past tense of the verb Stringere = To tighten.

But TestaStretta translates better as 'Narrow head', relating to the valve angle which is narrower than the old head which I suppose could be 'TestaLarga' (Wide Head) and much more polite than Testa di Cazzo (D**k Head)