Ghostgate

What the hell is wrong? I have my boost set at 0.8 bar and every time I shift from 1st to 2nd at any RPM above 4,800 or so my boost drops to 0.2 and doesn't build. My boost also drops from 0.8 to 0.5 and won't build up when the RPM's get above 5,000 in 1st gear. Also, if I'm driving in a higher gear and downshift to a lower gear and punch it, the car won't build boost, hitting 0.2 and staying there. Instead I experience that screaming turbo effect and no boost builds. My mods include a Bonez downpipe, Kakimoto Racing Exhaust, Greddy Profec A Boost controller, Greddy FMIC, Greddy BOV and a streetported engine. I've checked the car for hose leaks and tears, but didn't find any. I'm afraid it might be something big like turbos going out or something. Thanks for any advice you can give me, fellas.