hey guys I need your help... when I push my car hard my car starts to DETONATE and i get a boost spike im running 16 psi my question is.. what causes to detonate.. and how bad is it..

im running my stage 4 from Turbo xs.. and I have the denson one step colder spark plugs. and Im running 93 octane.. Last night i was on my way home and i red line 3rd adn the boost was a 1.07 bar and shift to 4th fast and it give my a boost spike to 1.43 bar.. and the check engine flashed twise..

well what happens if the car detonate.. what will get damage.. or how bad is it..??