Re: Funny plastic white thing (vgolfw95)
Looks like a fuel reservoir. has one line from tank, one line to the tank, one line to the fuel pump, and one return line from the engine compartment. Doesn't say in the Bentley, but it just looks like what it says.
Tell ya what. I could tell yout o install a new coolant sensor, check timing (now that I realize that you changed a head before this happened), get out the old Bentley, voltmeters and check stuff, but I would take it to a pro. Unless you enjoy tinkering, but even now it is getting out of hand.