Type 4 motor with Weber 32/36 carb question

I have a 1970 Porsche 914. The original type 4 engine was 1.7L but I put in 2L jugs. I got rid of the fuel injection after a year of hassles. I put in a used Weber carb after rebuilding it.

My problem is that in the mid range rpm the engine will die. If I push past the mid range to the upper end the engine will scream. The fuel injection never had that kind of power. It starts readilly and idles fine. I'm wondering if this is a jet problem. Or altitude. I live at 8000ft altitude.

Thanks for any advice.