Help Please!!!

My g/f has a 95 beretta Z26 and for some reason at 4000 rpms it seems like the rev limiter is kicking on. It just keeps revving to 4000 and stopping... Whenever you drive it, at high rpms it wants to stop and die..it feels like the transmission is slipping kinda but its not. Someone said it could be the fuel pump..Well we replaced the fuel pump and it is still doing it. My girlfriends dad and I thought it might be a lobe on the cam but we arent sure??? If anybody has any ideas it would be greatly appreciated. Thanks alot!!

Thanks for your help guys!