I have chiari type i, surgery soon. Percoset 10mgx4/day wasn't enough. Insurance denied oxycontin. Now trying morphine ER 15mgx2day, but not enough.?

Underdosed. If 40 mg of Percocet was not enough then a starting dose of MS contin (morphine) of 30 mg per day is way to low. A proper conversion (equal analgesic dose) would be 60 mg of MS contin (morphine). Even that may be low, but your doctor could then titrate your dose up.
Get surgery. Sometimes no amount of medication can ease your pain before a surgery. It's best in those cases to proceed with surgery as soon as possible. Your pain management doctor can assist with tapering the medications after surgery.