Traumahawk
Mine has the same symptoms.
It will not run "with power" unless I cover 1 /2 of each air intake on the Y. (same thing as covering one full intake).
I cannot begin to list the things I have done, trying to resolve this issue.
If you can name it, I've have done it.
If you can think of something in your past experiences that might shed some light on this, that would be AWESOME!!
Well did some searching....and think I found your issue....are you still running the FP needles and floats at 17mm?
Even with a kerker 4-1, (I still had the stock airbox) they were way too aggressive. Even with 150 jets...and 1st clip from the blunt end, I was dipping down to 9.8-9.9 A/F when I was at 40 mph in 5th gear, and would suddenly go to full throttle.
I had good luck with stage 1 needles 2nd clip from the blunt end with the above set up. When I would go to full throttle the A/F would drop to 11.0 and then climb.