mkrx

Hey guys, I have strange boost problem. When i fully accelerate to redline my boost pattern is normal. But when i change gear or take my foot off gas pedal and push it again, there is like 0,1 bar boost.. I have to take my foot off pedal again and wait for few seconds, after that it boosts normally again.. I thought my vacuum chamber was leaking but i tested it and it was fine, i also checked all one way valves? what could be the problem ?