After a bit of investigation, you are correct. There is no electrical boost pump. I did find a electrically operated, "Turbocharger bypass valve."
The first question(s) should be at what frequency is the noise being generated: Is it being received at the RF receive frequency (~27.00 MHz) or is it being heard at an audio frequency (20 Hz - 18,000 Hz).
To determine that, disconnect the antenna. Is the noise still prevalent? If it's gone then the noise is being generated at the receive frequency (~27.00 MHz). If the noise is still there, with the
antenna disconnected, then the noise is being generated at the audio
frequency (20 Hz - 18,000 Hz), in which case it's probably being
picked up on the power line (12VDC) in which case you should consider
bypass capacitors, chokes and definitely looking for bad grounds. In
the case of bad grounds it most likely would be loose or corroded
connections.
As far as VSWR is concerned, LokiWolf is absolutely correct; VSWR,
voltage standing wave ratio, is totally a function of a radio's
transmission ability and would have no bearing on the radio's
reception of noise, unless of course you're speaking of the affect
of a VSWR of 1 to infinity which would clearly be an indication of
no antenna connected to the radio!
As far as what's actually generating the noise you would have to
investigate what actually occurs when you engage the turbo boost on
your particular vehicle. "Something" is engaging electrically during
that sequence. Perhaps something to do with a change in the
transmission when it shifts into higher RPM's when you engage the
turbo boost?
Just my 2...and a half cents worth.