Dave,

Congrats on the "new" Vanagon!

The gas leak is most likely caused by the cross over vent tubing that run
above the gas tank. This is a common issue and the only way that I know to
fix it is to drop the tank and fix it. I think that most of the online
vendors have the parts you would need to repair it.

Dropping the tank isn't the most fun job in the world but I've done it once
and it isn't as bad as some say it is either.

As for the bucking that could be many things but I would start with the Temp
II sensor (this is the blue sensor located on the lower driver's side of the
thermostat housing). New ones are cheap and it's fairly simple to replace.
This helped me with my '90 Vanagon when I was having some similar problems.

If it is not the Temp II sensor that is causing the issue I'm sure that
others way more knowledgable than myself will chime in and set you on a
course towards fixing the problem.

Good luck!

--
Thanks,

Jeff
'90 Carat (Grover)
'86 (We call this one Parts)
'78 Bus (Melissa) Patty's Bus