1986 diesel 6.9 truck cold stalling

New fuel pump and injector O-rings installed. Clear injector bypass fuel lines installed. Truck cold starts fine but stalls within 30 secs or less and is very hard to
restart. After restart, runs fine and restarts fine all day. We can see bubbles in clear bypass lines that go forward up into the fuel filter, but only on the passenger side. Also, when we take the fuel tank cap off of the front fuel tank, lots of pressure escapes. Thanks for any help, doug
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