In answer to the queries regarding replacing the front converter on Series 3
cars with a test pipe: the answer is, yes, the “test pipe” will replace the
front converter, but it does NOT have a fitting for the O2 sensor. This
must be fitted additionally. Replacing the converter with this test pipe
does not affect the performance of the car, either positively or negatively
in any appreciable way (unless you have a plugged converter, of course, and
in that case, it is a miracle cure).This pipe is not legal in the US, which
is why it can only be sold (by SICP and others) as a “test” pipe. These
comments are from my own experience, as I have two S3 cars fitted with these
pipes and modified to take the O2 sensor.
Gregory Andrachuk
Victoria, Canada