2011 c70 engine stumbles between 2k and 3k

[Wardle3]

I have a 2011 c70 that idles fine but under a load it stumbles between 2k and 3k and then smoothes out again after 3k. It had a new Turbo put on a year ago and this month I put new plugs and coils and cleaned the maf. I can't figure out why it stumbles or stutters between 2k to 3k. Could it be the boost solenoid. It doesn't put a code out so I don't know what to try next. Thank you in advance.