I think coincidence. The correlation between cat failure and EVERY level of gas is probably actually evenly distributed, but running low/out is the only memorable association. 

My 2

Jim

On Oct 18, 2011, at 3:04 PM, mark drillock <mdrillock@COX.NET> wrote:

> A family member called about their Vanagon. Ran ok for a long time but
> recently ran it very low on gas. After adding some, it seemed low on
> power and much worse up hills. Running smoothly, just low power and
> getting worse as it is driven, barely making it up big hills. They live
> at 6,500 feet and everything is a hill.
> 
> Thinking bad fuel or stirred up debris in tank he changed the fuel
> filter, no help.
> Checked compression, all ok.
> Did fuel pressure and fuel delivery test, all good.
> Unhooked intake snorkel hose to air cleaner, no help.
> 
> I suggested he look at the cat so he did.
> All busted up inside into chunks.
> Removed chunks, power back!
> 
> Coincidence, or did running low on fuel somehow finish off the cat? My
> guess is coincidence but others have reported similar sounding
> circumstances.
> 
> Mark