In the late 1980s, Mazda diversified in the Japan market with the launch of three new marques. The company created Autozam, Eunos, and Efini, in addition to the Mazda and Ford brands already marketed there. This experiment was ended in the mid-1990s.
The Efini marque was a luxury-oriented brand. Today, Mazda continues to use the Efini name as one of the company's dealership chains, along with Autozam, but the vehicles sold no longer use it. This included the following vehicles:
The name is actually written with a tilde over the initial E, and can therefore be assumed to be IPA, the pronunciation symbols universally taught in Japan, and quite often used in product naming. The accompanying katakana (アンフィニ) shows the intended pronunciation in Japanese. A Google search for combinations of 'Mazda' with various spellings shows the following list, in descending order of popularity:
(8230 hits) 'Anfini': the normal (Hepburn) romanisation of the Japanese reading
(6170 hits) 'Efini': the IPA with the diacritic removed (most of these hits seem to be in Russian)
(1470 hits) 'Enfini': presumably a misspelling (or misguess) of the French, influenced by the 'E-tilde' of the IPA.
The cracks can't be seen unless you remove the tube and pry it open, and yet under boost pressure the cracks open up and vent your boost (which is sometimes accompanied by a loud whooshing sound from under the hood).
The Efini pipe also moves the air-bypass valve connection out of the air flow so it should breath a little better than the stock pipe.
Before measuring, I had planned to weld a flange onto the ASP pipe to match the Efini studs, but the height of the Efini flange face was too high to allow the ASP pipe's arc enough vertical clearance.