Thanks once again for all the tips, always educational!
I replaced the priming valve core at the filter. it's the same thing you'll find in your wheels. Mine wasn't very tight, but I replaced the core anyway, a bit tighter. Today the truck ran well without any more air bleeding. If bleeding should become necessary, the electric lift pump makes the process easier and a 1-man job. To other non-experts like myself: make sure there is fuel pumping before depressing the priming valve, or you'll just be letting more air in! Thank you experts for helping me with this problem. It seems like I might not need a injection pump just yet, but if it weren't for your advise I'd probably had bought one unnecessarily. -Jeffy.