I have a freshly rebuilt 406 - APR 195cc heads, rpm air gap, holley 650, comp cam solid 236/242 @50 501/510. 1.6 rockers(525/536lift), 10.8:1. Dart little M, Callies crank, crolwer 6" rods, JE pistons. 4 spd car with 4:11's.

I finally am done with my break in period and she runs great. Th first time I jumped on it she ran up to about 3,400 rpms and she start to break or or stumble. It does not fall on its face or bog down. It acts just like a reve limiter - it stutters at high RPM. I know i need to rule out fuel with a pressure guage under load - have not done this yet. I have electronic ignition (MSD). Bought a new MSD blaster 2 coild - did'nt change anything. I disconected my Suntac - no difference. Change my NGK plugs to Ac plugs - still does it. Any sugestions?

Do you have an MSD 6AL and still have the (as supplied) 3500 rpm limiter in it?

To me, it sounds like a timing issue for sure... that combined with a fuel mixture issue. In my opinion, while it isn't an opinion that should count for much, I think you are running lean with an improper timing advance/curve. Bugger-me damned if this anin't the case.

bad plug wire bad cap or rotor.

or in my case a few years ago loose MSD 6AL connection.
same symptoms as yours

Sounds like ignition to me . . . I know you said you changed plug brands but what about heat range? A cold plug will misfire like that -- I spent a lot of time troubleshooting a very similar problem only to find my plugs were too cold.

If it isn't ignition I'd look at valvesprings next.