Engine speed is absolutely determined by the amount of air taken in. Fuel only makes it work. A vacuum leak will increase the speed unless it ruins the mixture so much that the engine runs poor.

Always remember that the speed is determined by airflow and fuel in the right quantity allows it to happen. More fuel it runs slower less fuel it runs slower.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician