Dave, You said: ".......I installed a spring in the suction tube last week, so I can rule out the tube collapsing when warm" Try the following test. Disconnect the suction hose from the bottom of the pump and conduct your previous test. The high pressure high volume fuel pump needs unrestricted fuel flow through the pick-up line. The spring may be restricting the flow of fuel and or creating cavitation. DMC Joe Tech Information, DMC Joe Help Club, & Store "Summer Parts Sale" http://shopping.oraclesmallbusiness.com/dsvstore DeLorean Website Directory www.dmc.tv