Over the past 6-8 months I run into this issue in 4th gear that ends up limiting my boost from the usual 22Lbs to about 15lbs. It happens only in one specific instance, ever, and I'm absolutely baffled because it doesn't throw any codes or anything. It happens when I'm at WOT in 4th gear, and as it peaks into 4500RPM, a slight hiccup happens and then immediately loses the boost. It'll stay like that for about a day, and then like nothing, the power is back. This is only instance it ever happens, like clockwork almost, and never happens outside of those specific parameters.
Could it be knock? Limited power due to overboost(maybe piggyback related?) or Faulty sensors(MAP or Knock Sensors?) Hard to say because you'd think it would be more sporadic rather than at one exact instance that I can recreate. Either way, that's the next thing I'm trying to tackle right now.