shudder problem in '91 740 wagon-revisited

An update on a shudder problem I reported several weeks ago. When car is in
drive and slowing down and stopping at a stop sign or red light it would
shudder at about 500 RPM for a few seconds and then even out and move to
about 600.It was getting worse.
I had just replaced the plugs about 3000 miles ago when I got the
car(wagon). Last week I replaced the cap and rotor. The cap was all gunky
with red-tinged stuff in it and the mechanic said it has been arching in
back of the cap. we replaced wires also.
This did not correct the shudder.
Today I checked the plugs and replaced them with a Bosch Super plug.
Amazingly the plugs I took out had a gas smell to them-especially the back
2. One had a piece of residue on the tip.
The new plugs have corrected the shudder.
I assume the plugs were fouled and were causing the drivability problem.
Also, I rechecked the throttle body-had just cleaned it and there was a
small amount of red-tingled residue in it.
Is there anything else I need to be doing? I'm not sure what is causing the
reddish stuff to get in there in such a short time after cleaning the
throttle body.
Sorry for the long post.
Need assistance.
Thanks,
J. B.

 

Reddish stuff? That's odd, almost sounds like some sort of mold or
bacterial growth. If it's in the throttle body too you might check the
intake hoses, as well as the condition of the air filter if you haven't
already.

 

well, on second thought it's brownish liquid gunk.
I did check the intake hoses. and this brownish gunk was in there a few
weeks ago and I cleaned it. also, I changed the air filter about a month
ago. it was horrible then.
thanks,

 

The brown gunk in the intake could be oil blow by from the crankcase
breather.

 

yes. I thought that might be possible.
I had a new flame trap put in about a month ago.
I assume it is not gunked up but have not checked.
is this blowby a problem or somewhat normal?
thanks,
James B

 

Or from the turbo if this is one, some oil blowby is normal.

 

non-turbo