i agree the blower should make more than 5 psi on your combo.
in your other topic you mentioned it did make 8-10 at the start, that seems about right. you said it stared going down. i'm betting something mechanical is happening. odds are your bleeding boost off. make sure there are no vac leaks( can be hard to hear with the blower whine) and also make sure your not boosting the crankcase. with my blower i had to do away with the PCV and run open breathers to keep my dipstick from popping out.
dont worry you will get it sorted out, you cant just bolt this stuff on and expect 100% from it from the get go, you have to work out some bugs.
when i put my kit on i mis routed my PCV bypass kit, i was bleeding boost off to infront of the air filter. it ran alot better but it didnt start making boost until the higher rpms. i got all that sorted out and it CAME ALIVE.
also mention in yout other topic was the belt. you have it pretty tight. the
vortech bracket it pretty thin, when i put my blower belt on i get a big cheater and tighten it to where it starts bending the bracket, thats plenty tight, a slipping belt will not make as much boost.
EDIT, i just saw in your first pic. you need to take the line off that connects the TB to the oil filler neck, your bleeding boost into the crank case. you need to cap those off and run your PCV valve somewhere in front of the blower. or just cap it off and run open breathers.