Boosting a Mustang is pretty much the same as boosting any other engine, the more air you force into the motor, the more fuel you need to add. A 99 Cobra, depending on the condition of your car, should be able to handle ~10psi of boost provided the fuel system is upgraded and the car is tuned to make sure a safe air/fuel ratio is maintained.
__________________ Sometimes I think that government fits that old-fashioned definition of a baby: An alimentary canal with an appetite at one end and no sense of responsibility at the other.
- Ronald Reagan
Stangless...for now | 
Need supercharger ideas for 1999 Cobra 
