87 turbo II exaust problems
 

just but a apex GT systtem on my turbo II...not it is acting up really bad...the car is shacking , when i have it full throtle it takes a longer time to rev to high RPMS...the gear shirt is shacking really bad...there is a raddeling noise coming from behind the car...

what do i do...its a huge exaust and i want to keep it...what could be the problem