850 T5 Upgraded Now Boost Has Dropped Slightly?

I have an 850 t5 with hybrid turbo re map rIp kit other bits as well the car used to run 20 psI fine no problem until a couple of months ago now I can only hit 18 psI the RIp kit is only about 6 months old so I don't think it can be a boost leak through bad hoses but it's dropped boost pressure can any one offer suggestions to what's causing this also tried it with a cone type filter it's exactly the same

could it be some thing to do with the dump valve spring that was just a thought of mine or could it be some thing more serious