First of all, replace those Philips-head screws with SS hex head bolts. You'll be glad you did.
I've had the same problem with my IAB, but couldn't get mine lose enough, so had to replace it. Checking the IAB should be part of regular maintenance. Attached is a write-up of my saga and what I found. However, a stuck IAB should not prevent you from getting on plane, but it could. How much does your rig weigh fully loaded? BTW - the IAB baffles change position at 3950 RPM.
When reinstalling the IAB, check the IAB diaphragm as describe in the attached write-up and check the vacuum line from the IAB actuator to the IAB diaphragm to make sure it is fully connected and no holes in the tube. Low or loss vacuum can cause performance problems.
If you have an external fuel/water separator (which you should have), change that filter too. They do get clogged up. If you can't get your hands on a replacement filter quick enough, at least drain the canister.
You should also drain the VST. Water and gunk can accumulate there, too, and degrade performance.
When you pull the plugs, inspect them carefully. The firing ends should be the color of light milk chocolate. If all are sooty, suspect the HO2 sensor. If only one or two are sooty, suspect a misfiring plug or failing coil on those cylinders. Note: Often a plug will not fail until under high pressure.
Keep us posted on what you find.