Sooty - There is an issue with your set up. You might have a leaking or cracked wastegate, a partial blockage of the intake piping or something similar.

A standard T25 equipped CA is very hard to keep off boost.

Maybe you should buy a T25G which is only slightly bigger but will still allow you to run bigger boost and make some impressive power. But I would check everything before fitting it to find the source of the restriction.
Regards Matty