[89GT]

My 89 gt runs quite well (although not completely smooth) up to about 4800 rpm, then all hell breaks loose. there is huge vibration throught the car and engine abave 5000rpm. It seems to be mechanical in nature, like the timing was completely off. there was also the smell of un-burned fuel although i'm not sure this is related. It's also a little jerky at lower rpms. 1000-2000.
Anybody out there have any ideas?
Cheers!!