A PA46 turbo failed at 17;500 FT in cruise. The pilot was able to maintain 8;000 FT to his destination where just prior to descent the aircraft had a partial power and oil pressure loss.

Narrative

At 17;500 FT in clear weather; smooth conditions; I lost turbo boost to my engine and was unable to maintain my cruise altitude. I announced the problem to ATC but did not declare an emergency as all other power indications and temperatures were normal. I proceeded to my destination and was told to descend; but declined as I had announced all along the route; based on partial loss of power; my intention to proceed at the maximum altitude I could sustain; about 8;000 MSL; and then spiral down over the airport to a landing. Controllers told me they had passed along the word. But; the final inbound Controller told me to descend and I declined. He told me I might interfere with inbound traffic to a Class B International Airport but I had been given a Class B clearance and was in communication. I declined again. On short final approach to my intended destination; I suddenly lost oil pressure and made a direct descent to the runway without incident. The cause of the partial power loss/oil pressure loss has not yet been determined.