[Texasdoc]

I have a 351w newly rebuilt (400 miles) that has a miss above 4k rpm under load (medium to heavy)

Details:
Holley 670 vacuum secondaries
Mallory Hyfire 6AL ignition
MSD 8478 distributor. Vacuum attached to manifold. Advance all in by 2500 (one silver, one blue spring)
MSD ignition wires
New E3 spark plugs
Typical 1 1/2 inch oval Cobra air cleaner
Initial timing set at 16
Manifold vacuum at 14 in Hg at idle
Base plus vacuum timing is around 20.
Mechanical advance 21 degrees (total 37)
Vacuum port adds 8 degrees starting at 11 in Hg

Idles at 1k rpm fine. It pulls strong up to 4k rpm then starts to miss and loses power. Sitting in the drive way, hitting the throttle causes the timing to go above 40 total advance. I noticed that even hitting the throttle i am gaining vacuum, not losing -vacuum goes up to 22 while doing this. I'm not sure of the total because my timing light shuts off at around 4k (???). I tried retarding the timing so the idle advance (base plus vacuum was around 18 making the total advance in the drive didn't go above 38, but it did the same thing.

I also noticed that the secondaries don't open. I'm afraid to put my foot to the floor but do "get on it" sometimes.

Any ideas?