Infamous 2500 rev limiter problem on s13 redtop

[crazy9ceguy]

yep my car was running fine until today when i was driving home from school, went over some little bumpy road as usual then i noticed my car stalled. So i start her up again and drove it, but, the car wouldnt go pass 1500 rpms without shaking the whole car and running rich. in neutral the car wouldnt rev past 2500 rpms, its not the afm, I changed it with a friend and its the same thing, so which parts can be fucked up? this is a redtop in a s14 zenki. the car was runing for a year without problems.