I have a 7.3 powerstroke and recently I have had a problem where at times it is very sluggish, and sometimes I have no power at all, it will barely do 45mph and it blows a ton of white smoke and shakes like crazy, the fuel pump makes a loud gurgling noise when it is building up pressure to start.

I also have no problem idling after starting and it runs good for the first 100-200 yards

What could be my problem?

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Let me note it is a 2001
And it is not a head gasket, the smoke comes and goes and I have not lost any antifreeze