Hey guys I am having a issue with my car and I'm hoping you guys can shed some light on my issue. Here is the current combo on my car. It's a 2005 express Van lq4, s366 turbo, ls6 cam, ls1 intake, deka 80s, walbro 450 in the tank, -6 fuel lines feeding the car with a aeromotive regulator that's vacuum sourced in the engine bay. The car is running on microsquirt and I have the base tune provided from EFI source and I have been messing with it and I just cannot seem to get the car to run right. I am using a aem wideband, the analog unit, I have recalibrated the microsquirt with the correct values so the afrs in TS and the gauge are reading the same. So my issue is at cruise the afrs will swing all over the place, I am seeing it jump from 13-16:1 and it is causing a stumble that is so horrible and I cannot get it to stabilize. During wot pulls the car sits right at 11.5:1 at around 9 degrees of advance and it runs good above 100kpa. I have confirmed that there are no intake or exhaust leaks (there is a minor exhaust leak at the wastegate flange which is welded into the turbine housing, however when the car is at operating temp the leak is no longer there.). I have tried adjusting the timing during cruise to be one solid number and I have advanced and retarded it 10 degrees with no change. My required fuel is currently set at 3.15 and dead time is set at 1.3ms. I have adjusted the fuel till it was pig rich in cruise and adjusted it lean as well and the issue still is present. Now one issue I can possibly detect at this moment is how I have the fuel system setup and that I am possibly getting higher pressure at the fuel rail then I am getting at the regulator and that would make sense to me. I have my feed line from the pump feeding the stock ls1 fuel rail. And for a return to the regulator I have removed the scrader valve out of the fuel rail, used a -4 to -6 fitting then I have that feeding the regulator. I am wondering if maybe that small oriface at the end of the rail isn't able to regulate fuel pressure the way it should and is causing a higher the set fuel pressure at the rail. Does that sound like I am onto something? Has anyone else had this issue? I will try to upload some logs and the current msq when I have a chance, I just want to hit the ground running when I start messing with it on Monday. Thanks for all the help guys.