Hi. I'm sorry to trouble the experts here, but I'm a bit stumped. I have a brand new ZZ454 that I'm putting in my 69 Camaro and I'm having a bit of trouble with it. I just fired it up for the first time about 2 weeks ago(how sweet that was!). From day one, when I hit the throttle quickly, I get a pretty severe hesitation/bog and I'm having a bit of trouble determining the problem. Also, for some reason, it just doesn't seem like it's running smoothly. I notice a bit of vibration in the upper RPMs, but that might be something totally separate from the engine bog. All parts are absolutely brand new:

New GM ZZ454
Holley 750CFM, 4160, electric choke, vacuum sec, HLY-0-80508S
GM HEI distributor
Holley mechanical 110GPH mechanical fuel pump
MSD-8500 Super HEI Kit, with 6AL ignition and Blaster 2 coil
Taylor Thundervolt 8.2 wires, stock plugs that came with engine.

Here's what I've checked:

1. I have a fuel pressure guage located after the filter(which is clean) and it reads a steady 6.8 to 7.0. With 9.6:1 compression, the premium gas should be fine.
2. The carb is untouched out of the box. It's the 2nd new carb I've used with the same results. Fuel levels in the bowls look good.
3. Timing is set to GM's recommendations, 12 degrees BTDC at idle, about 36 BTDC degrees at 3000rpm. I timed it with the vacuum advance disconnected and plugged. The vacuum advance is now hooked up to the vacuum correct port on the carb(idle smooths out a bit and goes up a few 100 rpm when I connect the vacuum advance).
4. No vacuuum leaks(I've checked and double-checked), with vacuum good at about 12 - 15 at idle with my vacuum guage hooked up to the manifold port.
5. My PCV setup looks like it's hooked up properly.
6. I've used a second set of new spark plugs and wires just to be safe with no change in behavior. Gaps on the plugs are good(.045) and the plugs look pretty clean.
7. I've actually gone back to the stock HEI setup and coil just to be sure it wasn't the MSD setup and that made no difference either.
8. All my ground wires/straps look good and are touching good metal.
9. I've tried going around the distributor, removing one wire at a time but the engine dropped RPM consistently when each wire was removed(and it'll shock the heck out of you if you don't wear rubber gloves!).

The engine starts right up fairly easily and seems to idle okay(a bit rough though until it warms up in about 2 minutes). I notice a bit of vibration at higher RPM's(2000+), so I'm not sure if that's related(?). I can't imagine there'd be anything wrong with the long block itself. I was going to disconnect the new torque converter from the flex plate and the drive belts to check on the slight vibration, but I'd like to solve the engine bog/hesitation first. So I'm stumped on this one. I wouldn't think I would need to change the stock carb settings to eliminate the bog, nor should I have to move away from the stock timing settings. I was under the assumption this stuff would perform pretty well together right out of the box.

Any ideas? Your feedback is really really appreciated!!!

-Chris