Negative Pressure

[Aidsy1]

Hey guys, have just been reading up about the diesel vnt turbos etc, and noticed that it says that there should be no negative pressure (obviously because of no butterfly valve in intake). So can anyone speculate as to why, when my car has warmed up (sometimes does it on first start too) it reads -2 psi on my boost gauge (one that i installed) surely it should be at 0. I know it is only -2 psi, but the other thing i'm wondering is anyone has looked into changing the actuator or limiter screw to try and keep boost up and more boost at lower idle speed. Yes I know how dangerous this can be, messing around with the turbo, but I feel like there is a terrible amount of lag unless i boot it off the line. Any comments that people can put towards this would be appreciated. 

[yossarian247]

Although diesels don't have a conventional throttle butterfly many nowadays do have a butterfly valve in the air intake to regulate the balance of fresh air versus EGR gas being fed into the engine for emissions purposes. I don't know specifically if these are fitted to Toyota diesel engines, but all of the recent VW, Peugeot and Vauxhall/Opel diesels I've looked at have a butterfly valve in the air intake so Toyotas are likely to have one to. This, coupled with the fact the turbo won't be boosting at tickover mean than a certain amount of negative pressure is inevitable at idle I think. -2 psi doesn't sound like a fault to me.