topic summarises this nicely think headgasket ,its blowing out of the rad cap "new 0.9 bar"but it only does it if i give it charlie large i have also noticed it is a little flat as if its lossing power at the top end ie 5k plus.Its a my97 import with filter decat and scoobysport runs 1.2 bar boost. Any help pointers etc how much for gaskets etc. email me off line if you dont want your views made public.Tia Bob mac.

 

I would suggest a gasket is likely.
I just had the same problems on mine about 2 months ago (WRX STI4).
Cost £850 to me, warranty covered £400.
Gaskets are expensive about £300 (as there are 2 sides to scoobys engine), labour ditto.
I also had timing belt changed whilst the engine was popped, and had them check other things over so you could knock off £300 from the total I guess. BTW They skimmed the heads as well. Some places say don't bother skimming the heads, but IMHO this is just a silly gamble. If the heads are slightly damaged, skimming will fix. If they are damaged and they bolt it all back together without skimming it will either go pop again, or cause other medium term probs. Skimming cost £50 - so it's chicken feed compared to the rest of the work.
Don't drive it too far or get it too hot in it's current state, your asking for trouble if you do.