inconsistant boost???

[MrBtchy]

a few weeks ago i borrowed a boost guage off a mate to see what i was boosting. Generally the boost goes up to 8lb and stays there but i found that sometime(albeit rarely) it goes to 9lb and stays there. As far as i'm concerned there is nothing wrong with this.
However...after getting used to how 8lb feels i've noticed(but can't confirm as i've given the gauge back) that the car seems to have lost boost! It feels along the lines of about 4/5lb max and it doesn't come on till about 4000RPM. Now last week i had my car in the shop having the oil lines replaced with braided ones and 2 days later the clamp that holds the oil/water part of the turbo(don't know what it's called) came off and everything forward of the exhaust housing came out about 2-5mm.I thought i may have damaged the turbine but sometimes the the car boosts normally??!!
anyone have any ideas what could be going on? i know you're all going to tell me to hook the boost guage up again but this is a noticable difference in boost.

[decoy]

not sure about the damage, but is the 8-9psi relative to which gear you're in at all? or completely random?

[MrBtchy]

update...
8lb in first and second, up to 9lb in third(9lb is the highest it's gone and that was only once). no room in nz to try 4th or 5th(redline in 3rd is 100mph,plenty enough to lose the licence if caught.

to stop any confusion the engine is not in a starion, i've put it into an older car so i've converted from carby to efi...i'm not running a surge tank but will be shortly. i filled the car up 2 days ago and it started boosting normally! i might be wrong but i have a funny feeling my problem has to do with fuel pressure. i'll know after i let the tank go down a fair bit and see what happens with the boost.