Stroker Motor wont Rev pass 5200Rpm

Definitely try to see what your exhaust pressure is at max intake boost, even after you fix this issue. I increased my spring seat pressures by the IN and Ex pressures times the areas of the IN and EX valve diameters.. If you are buying springs anyway, might as well maintain the proper seat pressure for the cam, at boost. Area of a 2" IN valve is 3.14 x 10 lbs boost is 31.4 pounds of additional seat pressure to meet seat specification of cam.. Finding your cam specs is going to be interesting.
I'm not saying this is your problem as I, along with others, need more info.. Use any changes you make to establish a known baseline and enjoy!