Below is a great site for information. I purchased my 3.4 pulley from them.
http://www.scienceofspeed.com/products/S2000/

 

Yea I have read all that does not answer my above questions though... plus I have a vortech and SOS only has comptech pulleys. Would a 4inch pulley put me closer to 14psi @ 9k or would a 3.8? I know the pulley FAQ says it should be 14 w/ a 3.8 but have heard of people making more with the same pulley.

 

i have an ASP 3.5" pulley which was to be about 10psi but am reading 13psi due to test pipe and 3" piping on my exhaust...