I have a Tiico, which is similar, but not identical to your conversion.
Engines are simple. Fuel, Air, and Spark. I would throw in one other
factor...exhaust.
It sounds like you have looked at the first 3, but NOT the last. A
clogged catalytic convertor or exhaust system could account for your
problems.
If you had poor emissions and potentially poor fuel economy but
overall good power, then you could have a vacuum leak, or a bad O2
sensor, but with poor acceleration you are either not getting enough
fuel/oxygen, or aren't able to remove burnt vapors.
If the exhaust system is good, look at the fuel filter.

On May 27, 2009, at 9:18 AM, Dave Woolridge wrote:

> Hi All
>
>
>
> I am having trouble with my engine power in van.  I will try to give
> as
> much background as I can in hopes someone has some insight.
> Ultimately
> I know my real problem is with my mechanic and that I will need to
> go to
> another.  But before I do I want to have some inkling of where my
> mechanical troubles could lie.
>
>
>
> I have an automatic 86 Westy with a 2.0-L from a mid 90s' Jetta (GTI I
> been told).  For the first few years after the conversion, it ran
> like a
> rocket.  It could cruise up hills at 100 to 110 km/h on the flat the
> van
> would max out just over 125 km/h.  When cruising at 95 km/h I could
> easily get 450 km on a tank of gas.
>
>
>
> About 3 years ago I noticed it was struggling to reach 100 km/h on a
> hill and that was only if I could make a good run at it.  On the flat
> with the peddle all the way to the floor it would only cruise at 105
> with any head wind or 115 with a tail wind.  Now cruising at 90 I am
> only getting 375 km on a tank.  After several expensive attempts our
> mechanic (not the one who did the conversion) got it running right.
> These repairs included changing the plugs and wires, fixing an oil
> leak
> at the head gasket, replacing the O2 sensor, the throttle position
> sensor, the PCV valve and the mass air flow meter.  I had managed to
> drive about 3000 km, when I got a lot of water in the gas tank.  We
> used
> a VW shop in NJ to clean the water out of the engine.  The van
> seemed to
> run fine  for a little over a 100 km.  Then it became very
> problematic,
> losing all power and sputtering on hills, to the verge of near
> stalling.
> On that trip I unplugged the Mass Flow sensor and replaced the low
> temperature gauge.   I managed to make it home but the van had no
> power.
>
>
>
> Over the next driving season we did not use the van because our
> mechanic
> took over three attempts to install a new gas tank.  BTW: in the
> previous year when I suggested a hole in the top of the tank he
> refused
> to take it down and look, but offered to try several other fixes, none
> of which worked.  But I digress.
>
>
>
> This year I have taken it out and again no power.  We replaced the
> Mass
> Air flow meter $$$.  I was told it was broken but this had no effect.
> We then saw that the distributor was misaligned.  It was realigned and
> the van was back to acceptable.  Three days later it was gutless on
> hills.  So I thought maybe I should have the distributor replaced  $$
> $.
> Still no change.
>
>
>
> So here is my current problem.  I have no faith in this mechanic, he
> seems to think the van is fine.  I know another potential mechanic but
> he works with a chain and I am afraid it will cost $$$, just to have
> him
> "explore."  I am so frustrated with this problem I want to get rid of
> this van.  However, I know it can perform much better and this needs
> to
> be fixed before I can sell it.   Before I bring it to this other guy I
> am wondering what might be up, what can I suggest to him as a place to
> start looking.  Does anyone on the list have a 2.0-l conversion with a
> mid 90s Jetta who may have had similar power troubles?  Is it
> possible I
> am still suffering the effect of having water in the tank?
>
>
>
> Thanks Dave