Three days ago, after a cold start, my car stumbled for a few seconds as if one or more of the glow plugs wasn't working, then ran fine. I ran the car by the shop and my tech discovered some leaks around the fuel lines and on the lines coming out of the IP. No problem, replaced all the o rings, new serpentine belt, oil change. Picked up the car, drove home ok, ran fine all day.
Next morning, same problem, stumble at first start then everything ok. Took it back to the shop and while we were looking at it it started to run rough at times as if missing, revved ok but ran really bad at 1500 rpm. Then it became increasingly hard to start as if starving for fuel. Bubbles seen in both plastic fuel lines. Checked for leaks. No leaks, no codes, full tank, new filters, lines now clear. Car barely runs now, and once it starts after long cranking, it idles rough, and wer'e stumped.
Suggestions please.

Thanks,

Steve