When the car is in gear and you back off the throttle the ECU goes into DFCO (Decel Fuel Cut Off). This is a normal fuel economy measure done by the OEM's. Nothing is wrong with your car then.

If you are experiencing random stalling when out of gear and such. You have a few options

1) Downshift
2) Program e-mangle anti-stall

 

Reference for programming anti-stall

https://www.scionlife.com/forums/sho...d.php?t=168992

 

Also, the reason people were recirculating the BOV was because they had their MAF on the Turbo intake pipe, before the MAF. So when you enter boost then let off, the BOV vents and the MAF is reading air coming into the intake and you just vented that air into the atmosphere, and your car runs rich and possibly stalls/dies. That is the reason for having a blow-through setup. I would say it is your tune for sure man. It does look close, but it shouldn't really affect it that much I don't think.

edit: I didn't see the second page lol

 

biggest is 2.75 for piping size! not 2.5