Mikuni carb help just wont balance

[megabob]

Hi All,

I'm running Mikuni PHH carbs on my AE86 and i've been trying to scync them up for some time but one is not inducting correctly in idle and low throttle (makes a sounds like it only runs on 3 cylinders) but as soon as you put the throttle down a little more it pulls great.
using a syncrometer i measured the air flow and from front to back on the engine the first 3 cylinders induct at the same rate (5) but the 4th at the back only inducts at 1.

i'll give you a list of things I've already tried:
- rebuild both carbs
- checked compression on all 4 cylinders
- checked for air leaks
- rebuild the throttle linkage

I did swap the carbs around to see if the issue followed the carb but when i did that all the syncrometer readings were off but only slightly by about 1-2.

I'm really scratching my head trying to figure this out.