Thinking about what I wrote above... I probably over-simplified
the situation. The standard gauge sensor reads pressure in the
main oil gallery. Pressure in the gallery is due to the resistance
caused to the flow of oil, caused by it having to squeeze out thru
bearing clearances.
If you bleed oil off from the gallery, you will, to some degree, drop
the gallery pressure. By how much, depends on the percentage of
the total gallery flow that you divert to the turbo. If you are using
a small diameter orifice in the turbo feed, then the effect on gallery
pressure would be minimal.
The only way you would get a big pressure drop at the gauge
sensor position, would be if the oil to the sensor was passing thru
a small orifice
before it reached the sensor. Sometimes this
is done to reduce pulsation at the sensor.
Anyways, I'd go with the sandwich sensor block as mentioned above.
Then you will have a place to fit your oil temp sensor as well
Cheers... jondee86