Mark McCulley wrote:
>

> Have you checked thoroughly for vacum leaks?

Greetings.
 Sorry for the delay in responding Mark. Yes I have checked for vacum
leaks. Every conceivable place that could leak. Evey time a technician
looks under the lid they remark "sounds like a vacum leak" but none to
be found. Picked up a can of Liqui Moly Vacum Leak Detector, will show a
drop in idle if a leak is there. Not as messy as WD40 etc. No leaks
detected.

> It might be helpful to hook up a voltmeter to the output of the O2 sensor

Hooked up the meter to the O2 sensor plugged in. Ignition on .45V .With
engine started it slowly rose in a uniform fashion until the sensor
kicked in and appears to be operating fine. Lots of cross counts from .2
to .8

> You can also measure the "dwell" on the idle stabilizer

Haven't had a chance to try this. Have to find a copy of Probst' book.

> >downshifting, back pressure.
> What exactly do you mean by "back pressure?" Is your catalytic converter
> shot?
By "back pressure" I mean de-acceleration from a high rpm, 4000 or so.
The exhaust manifolds seems to push a lot of pressure which I am sure is
normal, but there is a strong vibration when this happens. The "cat" is
only a few months old, but muffler has a small hole and it sounds like
the baffles inside are coming loose. Can the muffler cause a strong
vibration?
Other problems are surfacing, but its late, so I will continue on
another day. Thanks.

Randolph.