more than likely you had a massive boost leak somewhere and you replaced the charge piping which has removed the boost leak.

 

If I had massive boost leak somewhere in the piping I don't think that the car could handle the big map, boost like 21 psi, overboost to 26 psi and then tapper to 20 psi

thank you though

I think my tuner has to control the boost somehow! even though he try and set the WG to 0 but car still overboosting.

 

With the newer piping that's more optimized for flow(in terms of diameter, degrees of bends etc) you now have less resistance on the compressor side of things making easier work for the turbine so you effectively need less exhaust pressure to produce the same amount of boost, which, in turn means you will have to bypass more exhaust which brings us back to the wastegate.
Assuming your tuner knows what he is doing and the boost is still unable to be managed at lower levels the best solution for this would be to go to an external setup. If you run two maps with different boost levels the TS Compgate 40 is a great do all wastegate. It has similar flow capacity to a Tial 44 but retains the smaller valve diameter which will benefit you when running the higher boost map

 

Thank you very much VIIICE. Great explanation! I will talk to my tuner if he can manage lower level of boost. If not then I will might go with external setup, so I will have to check this TS Compgate 40.

Again thank you very much...you are the best!

I will let you know what happen