RNR sells down pipes that are "O2 eliminator" style.
I removed mine and cleaned up the casting flash, opened it up a bit and gasket matched the entire hot side (with the exception of the head to exh manifold, gasket is purposely oversize). Spool up and top end improved, also I just removed it after 16K miles. Everywhere I cleaned up and polished was clean, the places I didn't had a good amount of carbon buildup. I can assume this carbon build up will cause some small amount of restriction to flow as it builds. I will now clean up the entire track of the exhaust flow.
I was really suprized how crusty the nozzle area was on the turbine housing. It had casting flash as big as .5mm directly in the flow of the exhaust where it blows onto the turbine wheel. I used a hand file to clean this area.

 

Use PB Blaster instead of wd40.

 

I have heard the exact same exhaust setup as mine with the only difference being hte o2 housing.. i think the 02 housing just gives it a bad *** sound as well..... car sounds crazy at idle and when the wastegate is opening.

 

well i used both wd 40 and PB and it didnt help, i broke one of my bolts!!! can any body help me out on how to take the turbo off?? also is it a hard job

 

well, it's simple. If the 02 housing is the 2 in the 4-2-1, then it's obviously gonna benefit the flowing of the exhaust gas when the housing is bored out and is larger.

Maybe I'm missing something, but it's the same principle of having a larger diameter exhaust piping.