of course.. but being a 4-1, it only does it for the upper rev ranges.. I bought it since I planned for a B20B down the road.. as most people here would attest, the 421 is the best for B16A. And after installing, I actually ran lean on the upper rev ranges, as the plugs started showing whitish tips. Of course, that was easily remedied with a VAFC, and an adj. fuel regulator. VAFC to reduce the fuel enrichment for the lower rev ranges, the fuel pressure to increase at the upper rev ranges.. the reason being that VAFC cannot enrich too much, as it advances the timing as well due to the way it works by manipulating air pressure voltage, and also the fact that too much fuel would actually make the manifold pressure read positive, which would cause a check engine light to turn on.
Dunno about the rest, but from what I've read from american mags from the old days, the manifold term can actually be used for the intake as well, where they call it the intake manifold, and the exhaust being the exhaust manifold. Ditto for the header term as well.
not very sure though.. it's been quite a while since I heard the term being used for intakes.
