A roots blower is an air pump, restrict the inlet or restrict the exhaust and it won't produce boost. Your not going to get boost until you open the butterflies and put the motor under load. I'd increase the drive ratio to 1 to 1 even with 8.5 to one compression and make sure I have good gas and a conservative advance in the ignition. The motor will be lots more fun to drive and won't self destruct unless you ignore any detonation signs. Remember this is street driving and your full throttle time will just be 2 or 3 seconds at best.
If you want to check the blower condition take it off and turn it upside down and check the clearance with a feeler gage. Bottom should be about .006 minimum and most street blower should be .008 with .012 needing to be refreshed by a professional. The timing should be .011 between the rotors and look at the condition of the rotor tips also for damage. My guess is you should try and up the drive ratio and give it a try! Gary Roushkolb Superchargers.