Usually hit peak 20psi falling back to 16psi at high revs
for the last 3 days its dropped to 17psi droppong back to 14psi

Today it seems to be fine again, only testes for about 20 mins though. Could it be to do with the weather ? I live Hampshire and drive a MY05 STI PPP.

Any ideas ?

 

There,s a small thin rubber pipe that comes off the the air box to turbo pipe then goes to the inlet manifold check to see it as,nt come off the inlet manifold if it as it just push,s back on

 

Cheers Mate, I will have a look tonight (with a torch) or wait till the weekend when I can get to the car in daylight hours. Are you able to post a Picture on here to show me where you are on about ?

 

Sorry i can,t but if you look at the centre of the inlet manifold theres a small core plug in the middle ( which is a small round disc)just to the left of that theres a thin black rubber pipe just make sure its pushed all the way on. My03 WRX lost boost and it was only half way off. Hope this helps. Gaz
P.S just looked at mine theres two the one that came off mine was the 2nd pipe from your left as you are looking at it

 

cheers mate I will have a look

 

Checked Pipes (I think) everything seems sound and in place under the bonnet. I have come to the conclusion it is an irratic fault, as it can both be ok and then low on the same day. Yesterday it was ok all morning, then I went out in the afternoon and it was low again. Dealer said nothing to worry about but had no idea what may be causing it. It's about 15% drop off which I consider quite a lot, what say you lot ?

 

Is the car always at max temp? The ecu maybe holding back some boost to protect the engine if its not seeing enough temp

 

That's what is really strange, when the car is just warmed up it seems ok, when it has been going for some time and has been up to temp for a while, that is when is seems to have less boost. I have ruled out weather conditions now as it can be good and bad on the same day only a couple of hours apart.