So this is my current issue. I swapped out plugs with no affect. Today I switched back to stock diverter valve with GFB. Problem persists and with GFB peak boost is only 22 from normal 25. Car is strong except for this. I'm hoping it is the WGA. I'm going to flash back to stock tune tomorrow but that tune is so bad that even if it doesn't do this it still has other issues that make for a bad driving experience.
Chainringtattoo: I think I am having the same issue as you as it appears in the video. I have a manual Abarth, EC P1/P2, EC IC, EC V4, and GFB DV. The car drives strong, but appears to boost dump slightly - I get three consecutive sputters when I am accelerating hard in second gear in Phase 2. I still feel it in higher gears, but less noticeable. It doesn't seem to boost dump at all in Phase 1 or in first gear in either Phase 1 or Phase 2. Did the Forge Waste Gate Actuator fix your problem?
I need to fix this. It is embarrassing when you leaving a Mustang GT in the dust and the car starts hacking up hairballs.