Serious boosting problem

Alright i know i ask you guys for help a lot, but i dont unless ive scoured the forums for posts similar to what im looking for.. nothing hits it right on the head, but any help anyone can offer on this would be appreciated.

when i step on the gas and get it going, it moves fine, and everything runs alright until i start generating boost. in 1st gear i can get to about 5psi before my car's exhaust / engine noise changes from a nice even rev sound, to a sort of buzzing noise. when this happens the car immedietly stops building power and speed and just stays like that with intermittantly jerking.
in 2nd gear i can reach 3psi, and from 3rd on i can barely make any boost with out this going on.

Ive gone through a lot of things, but i as always want some more opinions on this just besides mine

ive cleaned my MAFS sensor
and ive Checked plugs ( which were completely black from running so rich i guess ) and cleaned them

ive gone over my system for any boost leaks but cant seem to locate any, however i have a ring of oil around my BOV fitting ( which ive had for a while ) ill take a pic of it tommorow to show you guys to see what you think.

im guessing it could be my fuel pump if its none of the above? im still running my stock 240sx pump, would fuel cut-off cause this sort of problem?

BLOWN TURBO...

check it.

just checked the shaft play, seems normal.. anything else i can look for to tell if its bad?

what happens when u rev the engine? where is the sound coming from? (open the hood and manually rev the engine using the throttole cable)

The sound only comes when im driving, i can rev freely in the driveway, and my BOV still gives off some boost, so im not quite sure its the turbo. though there is a weird sound when i let off the throttle, coming from the exhaust side.

When im driving, and i get on it everything is fine, i can hear my turbo spooling, kind of like a wheezing noise. when i hit signifigant boost its like the engine just refuses to rev, and makes a weird noise that i can only describe as a buzz, but it more or less sounds like the engine revving up and down very fast. when i do this in 4th gear at a low speed, i can actually feel the car shuddering from this.

which makes me believe it could be the fuel system maybe? possibly not getting enough gas to keep going. anyway to check the fuel pump? maybe injectors?

I would also check the wastegate my brothers car would boost 1st and then boost almost nothing the rest of the gears and the car sounded like crap. We found out his wastegate was bad...put a new one on and the car ran great.

The sound only comes when im driving, i can rev freely in the driveway, and my BOV still gives off some boost,

do u have a boost gage? what r u boosting and can u sustain the boost when ur driving?

i don't think its an electrical issue, it sounds like a mechanical issue.

Fined out where the sound is coming from, ( how is ur transmition?)

do a boost leak check, seriously, its important.