The O2 sensor is only used on engines with catalytic convertors.  The
pre cat Bosch fuel injection system is quite capable of giving accurate
fuel mixture in operational service.  The O2 sensor's main function, IMO
is to safeguard a too rich mixture and thus a cat meltdown.

IMO the reason a the vanagon horsepower rating drops from 95 to 90 is
that the O2 sensor loop or rich lean cycling means that the engine is
running lean half of the time. The rich side of the loop is at .75
volts, while max power is at .84 volts of O2 sensor output.

It is impossible for a Digifant O2 sensored fuel injection system to
provided more power than a non-senosred digijet, because the digifant
will never set optimum power fuel mixture, while the digijet system can
be set to deliver optimum fuel mixture all the time.

Sincerely,

Mark Keller
91 Carat
Cowichan, Bay B.C.