As i said........
As the introduction of i-Vtec are to compete and the able for
engine/Variable Valve Timing open up even on lower rpm(adaptively
and more elctronically control) like the toyota VVT-i instead of
the usual more fixture(at certain) high rpm requires by Vtec to be
open for the extra boost or kick.
i-Vtec and VVT-i are certainly more fuel efficiency as it was
electronically control.... just like Electronic Fuel Injection and
Carburettor.
SIR engine is powerful compare to other are because it was achieved
by thorough tuning such as human forged and polished pistons and
lightweight components compare to Accord i-vtec which are factory
mass produced with standard components(cheaper engine
cost).
Currently the more powerful version for toyota engine are the
VVTL-i that ranges from 1.8l Celica SSII engine that are 190hp to
Altezza 2.0l 210hp. These engines are not mass produces and things
are done to the inner parts of the engine which are not visible by
factories at Yamaha.
High power Vtec engine are certainly specially done, the above
information are derived from AutoZine article.
8 yrs ago 20valve 1.6 toyota engine 4A-GE 20v are creating some
170hp.... This is the most powerful and well know 1.6 engine THEN
at Japan and was cap in a Levin, Trueno and later on AE111
Corollas.