Hello everyone, I’m a bit stumped on what my problem could be. First turbo works perfect but after 4k when it transitions my boost falls off to 1psi and a venting sound is heard but not a buzzing or whining sound like a boost leak. I have made sure to triple check the vacuum lines going to the correct places. I vacuum leak tested my intake and everything checked out. Any help is appreciated.

 

check if your charge relief valve is not closing. if its not then its just dumping all the boost.