Thermo and Cold start help it out when it is cold, I dont think they do anything when the engine is warm. I would start maybe check O2 sensor. I have an 82. Air Cooled.
 
Have you tried posting on Samba too? May be more Air Cooled guys there, though this seems like it should be some what unviversal question.

 

> Date: Fri, 4 Feb 2011 19:24:55 +0000
> From: greentabe-vanagon@YAHOO.COM
> Subject: Help with troubleshooting a 1980 Westy
> To: vanagon@GERRY.VANAGON.COM
> 
> I got an email from a vanagon guy in trouble so I'm going to take a look as soon as I can reach him. As I recall the FI is more or less the same in all the air cooled models, but I haven't touched an air cooled in many moons.
> 
> Summary: Starts fine cold, runs poorly when warm. Without looking at it, it sounds like it's running rich when warm. I'm thinking cold start valve? temperature sensor?
> 
> Thanks for ideas.
> 
> tabe johnson/90MV
> 
> *** email starts here ***
> <edited for brevity>
> 
>     We decided to bring it to a shop in Calgary (Concept1) to get it looked at before we hit the Rocky Mountains!    They tinkered with it for 4 days.  Checked the timing, set the idle and got it running pretty good.  They suggested that we get the Air flow meter replaced because it was on the fritz.   
>     When we got to Lake Louise, the Van started to run the same. Idle very low, surges on the highway at high speeds.
>  
> Installed a new AFM. Considering replacing the throttle body.
> 
> These are the things that I have replaced very, very recently.
> New Fuel filter (canister style), ignition coil, new cap, rotor, plugs, wires, battery, air filter,
> Air Flow Meter and ignition.
>  
>    Right now the van will start no problem, cold idle nice and happy, then when warm, chug, chug, chug and stall.
> 
> ***end of email***