Arg.

I posted a while back about how my van was stuttering and jerking when decelerating.  I adjusted the timing and thought I'd solved the problem, but it's back again.  Today I got caught in a rainstorm, and the problem got way worse.  So much stuttering and power loss that it was hard to drive home.  Again, the problem was most prominent when decelerating,

I'm getting pretty frustrated with the thing.  

The van is an aircooled california version.  Can anyone suggest where to start with with this?  The ignition system is mostly new, and the double relay is new.  

Any thoughts would be apprecaited.

Cheers, 
Greg
1982 Westy