I have ob. Sleep apnea & am using a cpap nightly. I sleep 8-9 hrs/night. Still tired. Sleep studies also show alpha wave intrusion. How is this treated?

Other causes. Alpha wave intrusions have not been shown to be a problem by themselves, and do not need treatment. Assuming the CPAP is set correctly, controls the apnea, and you are using it every night all night, i would look for other causes of sleepiness (including narcolepsy and idiopathic hypersomnia). Sometimes sleepiness from sleep apnea gets better with CPAP but not completely, and stimulants may help.
Stimulants. In most cases of sleep apnea, CPAP treatment does not completely eliminate sleepiness. Stimulants can be used if symptoms remain a problem. Other issues can contribute. Your sleep doctor might have more answers for you.