when i mash the gas it takes off as normal but after about 5 sec. the boost drops down to 7.5 then rises back to 12 and back down continues to to this up to the shift. it does his through out all 5 gears. now if i hold the pedal half way i boost to 7.5 and it stays there till the next shift. if i continue it has the same resolt through 5th gear.

 

boost leak? check vacuum lines and the intercooler coupler

 

I'd reset the ECU if you haven't already...

 

if there are not leaks maybe check the boost control silnoid it maybe going bad.

7.5psi is wastegate pressure.

 

vacuum leak, not enough pressure to hold your wastegate shut in order to hold boost.

 

Ok When You Say A Wast Gate What Is It Im Not To Falmilar With It

 

wastegate: Information and Much More from Answers.com

 

sorry i was pretty drunk last nite when i posted that up.. the problem is still most likely a vacuum leak which is causing your wastegate or BCS to not properly regulate boost pressure. It could also be a faulty BCS as previously stated tho.. i would start the car up and start checking your engine bay for loose/cut vacuum hoses to begin with.

 

I bet the uppipe has come loose. It seals and opens during shifts.

 

Im confused. You say if you just hold 1/2 throttle you are only getting 7PSI of boost, that sounds normal to me, wont hit Peak Boost unles you are WOT.

On the other hand the boost spiking to 12 then dropping isnt normal if you are keeping the pedal WOT.

- Mike