I agree with phunkdocta - the standard coil is not the problem. I ran 12psi and 8000rpm on my old A14 turbo with standard coil, standard points dissy, and standard mech fuel pump.

I tend to think your overboost theory is more likely. Try adjusting the wastgates to 9psi and edging up till your limit of 10psi is reached without any cutting out. Although that's probably not so easy to do wit the TT setup either...