Has anyone had luck swapping Frybrid solenoids for the ones supplied with the GreaseCar kit? Wouldn't be too complicated, would it?

I'm pretty convinced that the solenoid design is the root of the air-in-fuel problem I'm experiencing. I contacted GreaseCar and they sent me a new solenoid, but the problem persists. Everything is operating as it should, but air is still leaking into my grease fuel line - I cannot find any problems with the installation, nor can my mechanic - and he has plenty of experience with these systems. He also mentioned that GreaseCar has changed the solenoid design - could the 'new' design be the problem? The older GreaseCar system on our VW has no such solenoid problem - in fact, it works perfectly. That's why this problem is so frustrating.

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Autos:
1991 350SD 276,000 miles
2001 VW Beetle TDI 115,000 miles

Horns:
1955 Selmer Mark VI Alto (55,xxx)
1958 Selmer Mark VI Tenor (85,xxx)
1964 Selmer Mark VI Tenor (125,xxx)
1967 King Super-20 Tenor (430,xxx)
2002 Selmer Series III Soprano

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