why is this happening ?

[genesis]

finally decided to chip the car today spoke to simon from upsoloute
and arranged fitment everything went fine with the fitment and i must say he seams a genuinely nice guy.
took it out on the road for the first time after been chipped and i could hear a lot more turbo roar very impressed by how the car has changed but im noticed something else as well!!!!!!!!!!!!!!!
when you first start the car and warm it up then give it its first blast of boost the car is fine but after this there seems to be no pressure building up at the turbo all the induction roar has gone and the car feels flat ................. but turn off the engine for a few seconds and then turn back on and the original wallop is back .
i have only had the chip a day and it may need time to settle down but i am also wondering if there is a problem ......
so ill ask if any of you guys know any answers or similar experiances and if so how do i cure them the engine code is auq
thanks

[Sim]

I have had lots of problems with the N75 valve. I got nearly no power increase after chipping, then replaced the N75 valve. Car still does interesting things, and i feel that it definitely could be more powerful. Adjusting the N75 valve would bring back some more pressure, but i am very afraid that i will break it.

Maybe your problem is also related to the N75 valve, which mainly controls the boost. For example, when N75 valves get hot, their adjusting screw (or something inside) get stuck and i have to wait until it cools down to do fine tuning on it. Maybe your N75 valve gets stuck when hot, and cannot open to went boost from wastegate, so your turbo automatically shuts itself down. Never heard happening it before - have to admint, but after all the torture i've been thru with my 20VT, i can now imagine anything... If i knew, oh god!

May worth to try an N75 test with a 1551/1552/VAG COM exactly when you feel your car is not boosting. Switching into diagnostics mode, ECU will switch the N75 valve on and off all the time so you will be able to hear it clicking. If no clicking is heard then your N75 valve is bad!

[penaaz]

might be that when you first boost, goes fine, then you boost goes over maximum and you car goes to limp mode (0.5bar pressure), and it
wont go anymore so fast.. better to check your ECU for error codes.

[Sim]

Yes thats a quite reasonable answer, i wish mine would go into limp mode because of too much boost.