Vac/boost Source

[XGTRX]

So long story short, I have been cleaning up the brothel of an engine bay and analyzing and fixing up the poor attempts at many things.

Anyway, I noticed the Vac line to the fuel reg was T-pieced 3 times.

So I ran a new hose to the reg from the (Blue arrow) and fuel pressure gauge shows good pressure (same as before).

Then ran another hose to the EBC Map sensor and aftermarket mechanical boost gauge from the( yellow arrow) and the readings are horrible. Went for a drive to test everything and with the throttle shut the gauge reads 0 psi, as I open the throttle it goes into vacuum as per normal and as i come onto boost the gauge shows lower positive pressure and the gauge needle moves erratically.

Then I changed the source to the plenum and the readings were fine but no Vac of course.

Can this (yellow arrow) source be used normally?

Is there another Vac/Boost source? Can I screw a vacuum nipple to the (green arrow) and is this a reliable source?

Thanks

Edited May 27, 2016 by XGTRX

[GTSBoy]

I think the yellow tap is ported vacuum - meaning it is actually just on the upstream side of the throttle plate.

The correct location for sourcing post throttle manifold pressure signals is the auxiliary manifold under the main runners.

[XGTRX]

I think the yellow tap is ported vacuum - meaning it is actually just on the upstream side of the throttle plate.

The correct location for sourcing post throttle manifold pressure signals is the auxiliary manifold under the main runners.

Is there a nipple there that I can use or does one need to be tapped.

[GTSBoy]

It should all be there. That's where the factory boost gauge sensor sources its vacuum, the brake booster, etc. Look in the workshop manual.

[XGTRX]

Thanks