I had my car in a local garage to have the injectors changed while the plenum was off I got the garage to bypass the plenum water hoses and the EGR. Before the car went in the stock boost gauge worked fine now it is not working properly. When the ignition is off the gauge reads -14 when I turn the ignition on the needle jumps up to 0, when I start the engine the needle stays at 0 instead of being drawn back down to about -14. If I give the engine a little bit of throttle when driving the needle will move to wards the minus (which it shouldn't) side of the gauge briefly then start moving towards the positive when I give it some heavy throttle the gauge seems to work as normal moving into the positive side of the gauge but when I let the throttle off again it only come back to the center.

Would bypassing the EGR cause any problems with the stock gauge?

 

The car was back to the garage today as I thought it was drawing air they said they used some kind of smoke machine to pump smoke up through the exhaust into the engine to see if any smoke escaped but found nothing. Is this standard practice or are they just blowing smoke up my arse so to speak?

Anybody?

They got the vac hoses the wrong way round from the balance bar and the side of the plenum. This will also give unstable idle. Make sure the vac line from the balance bar goes to the boost gauge sender. The other two are a little harder to describe and are much easier if you get another Z beside to compare them...

There's two tubes and I bet they have linked the boost gauge one to the "other" one. Mine had a similar issue after the engine had been out to change turbos. It was also ticking over really rough but pulled fine. I remember they had colour marked the ends of the tubes to make sure they matched up again but they must have switched them at the plenum ends. I pulled them off one at a time while running to see the engine reaction and feel the end for vacuum on each. One definitely had real suction whereas the other not so much. I then switched those two at the back LHS corner around - the boost guage immediately came to life and the tickover settled down to a proper ultra smooth tickover it always had. The other might have been for the EGR.

 

There's a T piece too.

 

Have you a piccy of the connections or can you try switching them?