holley altitude problems

Ever since I moved to lubbock a little over a year ago I have been having fits from my carb. It is only two years old and ran perfect at sea level. It is a 750 80555s on a edel performer intake on a 455 buick engine otherwise unmodified. A few months ago it just started smoking black all the time even on easy takeoffs. I tried to tweek it then finaly jetted down 3 sizes. It seemed to make it better but not perfect. Now starting about a month ago it is doing it again but mostly on hard takeoffs. When I get going smoke cloud ( black smoke) blots out the rear view mirror. I went to the brown spring on the secondaries and I can't feel the transition anymore but they are there and strong as ever but smoke is still there too. This carb only has the metering plate on the back so what do I do to make it stop. Primary side seems jetted about right now. If I check the plugs after a week of my wife driving they are normal but after a couple days of me driving they are pretty black. She still hasn't discovered all the power of her sleeper car and never uses the secondaries.
I am thinking power valve or gasket leak but sure can't find a leak. Ar these symptoms like a blown power valve. It has backfired a couple times that I know of but is sopposed to have the new power valve saver.

What's your altitude there? I moved from Albuquerque about 2 years ago which is at about 5500-6000 feet above sea level. Trust me, I feel your pain!

You may want to look into your accelerator pump nozzle size and step it down a notch or two. Remember, you are dealing with less dense air at higher altitudes so that initial charge from the accelerator pump may be too much now. Your powervalve should still be ok. I still ran 6.5's on my holley even at 6000 feet, but again, it depends on the vehicle too. You may have to drop it down to a 5.5 or maybe lower depending on your cam and vacuum signal.

And just for good measure, check your float levels before you start anything else. Alot of times that ends up being the correction.

Hope this helps! ;)