DOHC1.8

Im having a boost creep issue with my boosted b20 daily. I have a 10 psi spring and my dumptube welded into my downpipe and its to a full 2.5 inch apexi ws2 exhaust. When its completely hooked up it will stay right at 10psi no problem. Then when I try to run open downpipe it creeps to 15 psi???? I originally had this same issue with a 7psi spring then put my exhaust on and i wanted more boost so I got the 10psi spring. Now im bored with it i want to run open downpipe without the spike. Has anyone had the same issue before?

TiAL

removing backpressure + not the best priority for the wastegate = that exact result