You guys are a trip!!!
This is something I really want to learn how to do so I plan to just keep practicing until I get the nickel look down. The welding forums are awesome, but not very helpful in specifically how to set the knobs on a Lincoln 140. But, never say die.
As for the boost leaking, you might want to check the WG spring... regardless of what is downstream, the WG should hold the pressure. Perhaps the spring is getting tired and not able to snap closed as quick as it should. the funny thing about mine is that after I removed the WG muffler, my gauge is showing .8 instead of .7 bar. So mine did the exact opposite. I am sure a dynamicist could explain that the spring can now react quicker with the lessening of back pressure on the WG but unfortunately the guy that I used to ask no longer works for me.
Bench racing is what makes this forum fun.