Turbo Blankets / Exhaust Wrap

I just got the stage 1 turbo, going on with my rebuild. Wanted to maybe go to the stage two but was told, I'd have to do more like injectors and a chip to work correctly or wouldn't work well.

 

Since we are on the exhaust/turbo topic, let me ask you all this, those who know : what are pro's and con's of going with the one inch bigger exhaust from the turbo? I have the 2006 isx and after the Vgt there is the reducer to the smaller exhaust, vs the Vgt exhaust size. My pipe is beginning to rust through so, I was thinking about changing the pipe to the same size as the Vgt exhaust port, diameter wise. Should I do it or not? Why? Why not? Thank you.

 

Reducer to a smaller exhaust? My 2006 ISX had a 4" flange pipe off the turbo that expanded to a 5" pipe at the other end of the flange pipe. The outlet of the VGT on the ISX for your year is 4".

 

is their mpg/power gain on exhaust wrap.=?