the boost drops due to intercooler core restriction it also dont help it being a twin pass intercooler you just need to turn the boost back up but not before getting it setup because it will be running leaner from the denser air from the cooler

but saying that if the pressure drop is to much (like the air tec intercooler) from core restriction you can begin to perform worse than before if the boost drop is high enough to negate any gains seen from temperature drops.