I own a 1999 300EX. It has been run hard everyday of it's life. I have come across a problem at high rpm. It sputters out and won't rev out. It is smooth and runs strong off the low end but when entering top end it will die off and jerk like a bitch. It isn't the cold weather because it has done this since summer. I would greatly appreciate it if anybody could help me out in what the problem is.
StrokerEX

 

maybe the cam is worn down and won't lift the valves high enough like it used to. this would explain why it has power on the bottom end and not the top. less air is taken in and expelled at slower RPM's. but as rpm's increase the gasses can't escape fast enough. hope this helps.