lt12 3 rotor breaking up
 

i'm tuning a 3 rotor with a lt12. at 5k rpm it breaks up, if i add fuel or minus fuel it does the same thing. rpmcrs i minus from 1% to 5% then add 1% to 5% at 4500 to 6000 rpm. same result. i messed with the wot settings same thing. changed the load settings same thing. afr reads 10s to 11s, at times i see 12s. the car is running stock twin turbos seeing 10 to 12 psi. timing is 23 deg. any help is appreciated thanks

Plugs are new also.