ive had this issue since I got the car in nov. if I am in part and rev the gas its smooth when im driving and I try stomping on it between 2k to 3k it sputters or even if im driving it and give gas to accelerate wile cursing. it almost feels like if plugs are fouled, but doesn't do it all the time. when I first got the car I changed the plugs and it went away ,then it came back. I thought plugs were fouled . I changed it went away then came back. someone was telling me its they coils. so I changed coils, wires and plugs again. like I says doesn't do it all the time, sometimes when it does it ,it isnt that bad. some times its just bad sputtering until I get over 3k

 

You have a split vacuum hose somewhere.

 

I don't hear any vacuum leaks, any idea where to look?

 

Check the vacuum hose behind the 2nd turbo actuator it will be real tight to get to just to let you know.

 

Actuator as in waistegate?

 

Correct the one towards the firewall it will be real tight to check it. I had that problem when i was one twin it stumbled felt like the 2nd turbo wouldnt kick in then it would clear up and the problem was off and on, i checked the vacuum hose and it was split i fixed it and all was well afterwards.