69 Mach 1, engine cuts out

Posting this here also, are ther 2 of these forums?

Am getting "cutting-out" at higher RPM, like the engine is running out of fuel. Doesn't do it all the time, does it more in second gear than anything (automatic car) but also some in first gear. Has Holley 750 Vac. Sec. (3310-3).We changed the power valve to a 45 (low vacuum at idle in gear), put in 75 jets (stock is 72), put a 28 squirter in (stock is 25?), and put the short yellow spring in the secondaries. We have verified the secondaries are opening while at full throttle even though the vacuum isn't the best. Was having another problem of a "bog" when nailing from a stop, but that problem seems more intermittent than the "cutting-out" problem. Have MSD ignition (6AL) with Ford electronic dist., advance is 14 degrees initial with 36 degrees total. The engine is Ford 390 bored +.060 over, heads are as stated above with exhause ported slightly and stock adjustable rocker arms, Holley 3310-3 with electric choke added, performer RPM intake, and 428CJ ehaust manifolds (headers were a nightmare on this car), Comp Cams 280 Magnum cam with matching lifters and springs, 2,500 RPM stall, 3.50 posi in the rear. Car is a 69 Mach 1 Mustang restored with just basically the engine changes I outlined. Please let me know if you have any ideas. Thanks!!

Scott