Rough Idle

After using B100 a 18 months ago, my 97 E300D started leaking everywhere. I made the Trip to So. Cal from Phoenix. So, I had an Indie shop in HB change all my original plastic lines, shut off, etc, etc > Changed. I cannot see any leak of Diesel, nor does it smell like diesel. The plastic line going from the Full Fuel filter to the shut off valve, I can see air bubbles. If you don't have fuel leaking, how do you determine where the air is coming from? Is there a sticky or a DIY on these Injector pumps.