Questions for Roots style blower owners????

[cranknut67]

I have a b&m 144 blower with teflon tipped rotors and I am currently pulling about 6-7 pounds of boost with it. I have the 2.66 upper pulley and the 6" lower pulley. questions are :

1. does the boost I am producing sound typical ?
2. instead of running 120% overdriven, to 160% overdriven, how much would I theoretically gain in boost? (trading up to a 7" lower pulley"
3 is there any place to send these in for a rebuild?

I am seriously entertaining the idea of buying another like 142 or something to put on the new stroker I am building, but would like to have the other one rebuilt and for spare...