Take heart, and be cool.  I know it can be a bitch and I have had this 
problem.  The thing is, I can't remember exactly what I did to fix it.  I 
even put a new motor in and it still did it ( it had the head problem and a 
bad main bearing, so it needed one anyway). I didn't have a fuel pressure 
gauge that went high enough, so I replaced the pressure regulator.  That 
didn't fix it right away, but after a lot of tweaking on the mixture 
adjustment, timing, etc., I was able to get it OK sort of.  Since then, I 
discovered a bunch of other things wrong and since everything effects 
everything else, as you change bad parts, the synergy becomes different and 
everything changes. I had a bad ECU at the time. It was new from VW.  I 
went through 3 of them before I bought a rebuilt from Bosch, and it's been 
going strong for  5 months.  I also replaced the air box since then.  It 
had a couple of small dead spots, but the temp sensor was more than 10 
degrees off and I didn't think anything of it but, I discovered that I was 
getting much better mileage on my Florida vacation.  It shows that 
everything has to be perfect or  it won't work right.  When I put that in, 
it worked much better overall and I was able to define the exact problems 
of each of the 3 bad ECUs (each had different problems).  It was then that 
I decided to go with the rebuilt ( I didn't want to buy another ECU if that 
wasn't the problem after all.  I SPENT MONTHS DIAGNOSING THIS ECU PROBLEM. 
 I HAD SEVERAL METERS HANGING OUT OF THE ENGINE COMPARTMENT FOR THE ENTIRE 
TRIP TO FLORIDA!!!!!).

Just keep this in mind, I haven't cursed mine in months.  I'm getting 
around 18 mpg (I even got 21 toodling in the hills),  I'm not saying that 
it runs perfectly...yet, but it runs pretty good.  I think that once I get 
around to replacing the aux. air regulator ( again) that doesn't open or 
close all the way, it may run  very close to the unutterable P word. 
       By the way, I'm running my timing advanced about 5 degrees with 
premium fuel and it has a lot more pep than at the stock setting.  Good 
luck.

Craig Rogers
Ineffable Audio Unity Inc.
P.O. Box 512
Riverdale, NY 10471
(914) 378-1606
mailto: carogers@idt.net

'85 Wolfsburg weekender.