We thought about putting a a/f gauge on, but didn't' thing it needed it after we found the problem still existed once the turbo was disconnected
How did you check the exhaust? Sure sounds like and exhaust leak.
What fuel pressure reg is on it. It might be a good idea to t in a fuel pressure gauge and watch it when RPMs come up.
Did turning up fuel pressure make it better or worse?
It is always a good idea to eliminate a tether, rollover valve, or any other aftermarket device that is tapped in to ignition or electrical system.Mine ran similar to that when I put on a Teth-Air wireless tether, was drawing too much power from somewhere wouldnt fire the secondary injectors properly. Never looked into the problem, just took off the Teth-Air and threw it in the garbage. Never a problem since.