Boost Guage Problem?

[mzfe5speed]

i hooked up my boost guage, it's T'd into the vacuum hose that goes to the boost actuator. it is a mechanical guage. at idle it reads about -15psi, cruising at 70 it reads about -10psi. the wierd thing is that at full throttle the max reading i get is 0psi, no matter what gear or RPM i pull from. why dont i get the proper reading of 4psi? do i have it T'd into the wrong vacuum line? or what else might be the problem?

[DatSRBoi]

dont tap it there.

[mzfe5speed]

^ok, so where should i tap it?

[Astro]

On top of the s/c there's a screw that you take out and put a 90 degree elbow fitting to attach the line for the gauge.

[scdsolara619]

look @ the pic

[mzfe5speed]

^^oh, so that explains the notch in the TRD strut bar!! thanks guys, i'll do that this week!