I've got a MY99 Turbo with full decat, ITG panel and a tek2.

I just had a blast up the A10 near me and stopped off at a McDonalds (brings back FRST days), anyway, I let it run a bit before turning it off to eat then started her up, walked around the car to dump the rubbish in the bin (thats the plastic bin and not the nova next to me) and proceeded off down the road to the A10 again, BMW 320 or something right up my ass, floored it, and it stayed with me, huh I thought! Checked the boost gauge and it read 0.5bar and wouldnt go any higher (guess that gives me about 170hp, tried 3rd and 4th, still same!) so I moved out of the way and trundled along feeling a bit worried and then opened her up again and she went and did so all the way home.

WHY? It wasnt particularily hot today and I really dont expect these cars cut to 0.5bar in hot conditions because nobody would buy them, whats wrong?

I've just had a new head gasket after it blew shortly after the tek2, so naturally i'm a bit worried still.

Ideas?

That's the 'safety net' cutting in - sustained det (but still only brief)causes it to drop boost to prevent nasty things happening.. It'll then return relatively quickly, usually after a ignition on/off/on cycle.
With the Tek2, unless you've got something like the APS cold-air induction kit, my guess is heat-soak to the intercooler - your charge temps were high enough to cause det. But that's only a guess :)

its using the cold air feed from the standard subaru air box, its not as if its using air from under the bonnet.

ok - standard air inlet - shouldn't cause any problems there...

When you floored it, was it not long after sitting idling for a bit? The heat soak can stay soaked in the intercooler for some time!
Also, it could simply have been a didgy batch of fuel. It happens!

Ahem, just thought of somthing else - quite possibly a dodgy MAF sensor. MY99/00 originals are the dodgy ones (the newer ones are better); when they are on their way out, they underread, so make the car run lean, so will make it det...

yeah it was shortly after idling for a while, perhaps the heat built up whilst I was eating my food, then a little idling and it all added up perhaps, I think i'll start looking at a better intercooler to be safe, I love these turbos in the winter (especially with awd) but I didnt have my car modded last summer so wasnt bothered as it was all warrantied, should I take it easy in the summer when its really hot? Today was a surprisingly hot day. Would a uprated Intercooler / FMIC help just in case?

This happens if knock retard is seen at a certain level for too long a period of time, the ecu drops boost control and leaves it to run on the actuator, probably caused by heatsoak in the intercooler, there are a couple of settings that can be adjusted to stop it happening so easily, contact your source and ask them if they can mod your ecu for you. Really you should not boost the car if you have been parked up/in traffic until you have traveled enough distance to get good airflow through the intercooler to drop temperature, sat like that could easily take temps into the 70's and 80's.

Ah i see, makes sense, would a better intercooler help this kind of thing a bit or some better hoses? It sounds like something which cant be eliminated but instead something which should be possible to reduce.

Heat soak will affect any TMIC to a point (and I can't see how one would be affected less than another, unless it also isn't as good a intercooler either...) which is one of the reasons why people switch to a FMIC - which also has the benefit of being larger hence more efficient too.
The way round it is to wait for a while after sitting till for a while :)

ok, thats put my mind at rest.

Will a uk car with tek2 and decat get much benefit from a FMIC then?