Eric,
My story is consistent with yours. After 18 months of frustration, I had my 4900 serviced by an authorized repair center;they replaced the pump unit for the same total price of approximately $500. The printer has worked beautifully ever since. If I need to do a power clear, it clears the head..simple.
The printer does make great prints; it is nice to get back to that...
Best Regards,
George