I just got off the phone with my colleague at Advanced Diesel Systems in Fresno, CA. They are a authorized Bosch service center for injection pumps. John confirmed that if there is a steady supply of fuel to the injektion pump, without air bubbles, the supply (or lift pump) pressure has absolutely no effect on delivery pressure or timing.

This supports the information I received from Gus at Pacific Fuel Injection in San Francisco.

John continued to point out that the only way the timing could be affected was if there was air present in the system during the delivery cycle. John was also quick to point out that is is a loss of available volume (i.e., plugged filters, etc.) that contribute to a power loss.

Hope this information proves interesting...Robert