The nut below the O2 sensor required a smaller washer due to the weld so it would lay flat. I was able to use the OEM nut with an open end 17mm wrench.
The nut below the wastegate tube was a major pain! I was able to use two different 17mm wrenches. One 6 point & one 12 point. On the bottom end, I had to grind one edge of the flanged bolt to slide into the hole by the wastegate tube.
Form Follows Function. If it doesn't work, get it the f--- out. A RaceCar Named Carmen
MFactory LSD  TEIN  Enkei 17x9 RPF1  Toyo R1R  Hawk HP+  Schroth  Corbeau  AWR  HotShot  Headers  Magnaflow  Side Exit 
i bought a Zebel O2 housing , it broke when boosting on the freeway. funny because i have solid engine/tranny mounts and a flex pipe in the exhaust. only owned it for about a month when that happend. mjspiess interested to know where you purchased the exhaust flange at? the five bolt flange.