Pulley size on m45 supercharger!!!!

[guiguilandry]

So today I was at the track and I did what I consider a not so bad time with my beater... the LD9 S/C....

15.071@91.27
60ft : 2.281
R/t of 1.031

Now I want better times... In the very near future I will recieve my hptuner and I don't know the pulley size for the M45 that give 10 psi ???

I heard 2,6in or 2,7in.. is it true?? I don't know shit about the m45.
and if I change the pulley size, do I need a shorter belt ???
for now the beater ( old car of Vinalero ) have :

Gm s/c kit
180* t-stat
H.O. alt, 200 amp
2,3H.O. TB 57mm
Pacesetter header
Straight 2in 1/4 exhaust with no cat or resonator, only a dynomax super turbo muffler
WAI, not yet a CAI, I'm gonna put the battery in the trunk ASAP
I'm running on radial T/A 215's at 20psi on the track
also I have a short shifter
Cm coilspring and GR-2 shock
Crossdrilled and slotted brakes...

I'm waiting for your opinions on what I should do next.... CAMS, PULLEY, N2O