is the car hesitating/missfiring before it cuts out at 16psi, what is it doing?
what size injectors are they?
do u have a rev/boost/fuel cut set on the ems?
are u running an afm, what type?
what CAS are u running?
what plugs/gap are u running?
we need info to help u

Do you have a tacho? What does the tacho do as it cuts out?
I have run well over that boost on a tired old Aseries points dizzy, never cut out from lack of spark. Always ran NGK spark plugs.
What are the plugs looking like? is it over fueling and the cdi just helped keep the plugs alive longer? When it dies does it instantly run good again when you back off?

im just running normal ngk plugs in it
its like the power cuts off and then runs etc
when i didnt have the cdi it did it running 6psi and ems said to put a cdi on it and after that it does it over 15-16psi
i might try a better MSD coil first and see whats happens
yeah if u back off it runs ok again after, its only when it start to hit around 5000rpms, it kinda feels like a rev limiter does

sure it isn't a bit of valve float?