Pierre , are you running a batch fire or bank? Batch would surely create a pulse but it would be a frequency, not a pulse as you are still opening them many times a second. I like the pulse damper idea, a sealed vertical air column of any size. Cavitation is murder on parts; think of an ultrasonic cleaner, same principle. It can eat a Part up.

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I didn' t buy it, I built it.....

The pulse and bubbles mentioned throughout this thread were with the engine off, pump on. I ended up putting one of these on it. It helped, I think some flutter was there and it comes/goes. I don't think it has that big an affect anymore on how the car runs, I found other problems. All this may have been for nothing but I did end up getting a better fuel system out of it I suppose.

A lot late, but some tech that others with external pumps have run into. Pishta mentioned it, cavitation, and Sam hinted around the edges of it, boiling fuel. Combine the two, cavitation due to boiling fuel. How to get there? Pull a vacuum on fuel and it's boiling point drops markedly. Like, say, in the section of hose between the tank and the fuel pump. Classic vapor lock in an unexpected place from an unexpected source. According to Bechtold's SAE book "Alternative Fuels Guidebook" (an excellent source of fuel related info) gasoline's various constituents boil between 80°F and 437°F. Presumably this is at Std. Pressure. I once looked up how the boiling point of gasoline is affected by pressure and the result was surprising. I wish that I recalled the numbers or could recall where that post is, but even a slight depression in pressure on gasoline lowers it's boiling point significantly. After seeing the numbers that vapor lock at altitude is so easy to have happen is no wonder. What is a wonder is that it didn't happen a LOT more often.

I've watched several late model engine swaps in off road trucks deal with this. Their situation is exacerbated by the operating conditions that can be quite a bit hotter than typical on pavement, and lacking the airflow that pavement usually has. The common fix is to go to an in-tank pump, but I think that they did so because by that point they're tired of fighting and the 'throw money at it' option is appealing.
If you reduce the restriction in the line from the tank to the pump the vacuum will not be as pronounced and the problem may go away. One thing to watch for, particularly in tightly bent hoses, is for the pump's suction to collapse and kink the hose.

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Thom

Cross-threaded is tighter than Lock-tite