Boost Gauge Problem Inaccurate Readings Please Help

[BioDieselVW]

So i hooked up my boost gauge and manual boost controller today. At first i hooked up the boost gauge to the nipple on the intake and installed the boost controller. The gauge was very bouncy and read 10 psi at wide open throttle. when i went to turn the boost controller up it read lower psi. So i turn the MBC to the lowest setting and i was getting 15 psi. Now i went and installed a tee in the actuator side and the boost controller to the tee and it only reads 8 psi with the boost controller at max setting. What am i doing wrong? Could it be a faulty MBC?

Here is the link to the MBC i bought on Ebay.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1,1&item=290031736699&ih=019&sspagename=STRK%3AMEWN%3AIT

[jtanguay]

if you tee into the mbc line you will see a little bit of pressure drop because the mbc will 'bleed' pressure off.  8 psi from 15 psi seems like a really big drop though... maybe your best bet is to switch to a smaller diameter hose, or use some type of restrictive tee.

that way less pressure gets bled.