For those who did not already know. I bougth this 1994 940 NA with 100k miles couple weeks ago. It did not pass smog test with an HC 50% higher than requried amount.
I started from flame trap. To my pleasant suprise, it's easily accesible on my 940 NA. I was able to pull the large hose off, pull the vacuum hose off, the pull out the flame trap housing. The flame trap itself became completely brown and brittle, but most of the small holes were not clogged. The vacuum hose to the intake manifold, however, was totally clogged. The nipple on the intake manifold was ok, but I removed and cleaned it anyway. The B&A flame trap I bought from Advanced Auto seemed to slightly larger than the housing. Trying to force it in and I made a 1mm wide crack on the flame trap housing. I wrap the housing with a layer of 3M electric tape and plug the large hose on. I am not sure if this will do any harm on the O2 sensor. Is there anything in the electric tape that might kill the O2 sensor? I had to run back and forth to Autozone to get a vacuum hose of correct size. They were either too lose or too tight. I decided to take the tigher one so at least it won't leak. But I might have to cut it off next time. Anyone knows the ID of the vacuum hose that goes from flame trap housing to intake manifold? After doing the flame trap and hose, the crank case finally developed some vacuum. With engine running, I was able to loosen the oil filler cap completely, it would dance all around but would not fall because of the negative pressure :)

The spark plug socket which I used to install NGK plugs on my Acura Legend was too small from the NGK plugs I bought from FCP Groton. So I ended up not changing spark plugs. I did measure the gapping, it seems all plugs had a 0.030 gap out of factory.

I then changed the distributor cap and rotor. The one on car looked fairly new. But once I took it off, there were some black gunks in the cap looking like some rubber stuff. The rotor took me a long time to take off. I had to pry it with a screw driver and fearing bending the distributor shaft the whole time.

The O2 sensor turned out to be a big PITA. I started soaking it with PB Blaster everyday since a week ago. It still took an 18 breaker bar and at least 30 minutes struggling under the car to break it loose. Then I realized I could not follow the wire and find the connector (I worked on a street, couldn't put the car on four jack stands). For one moment I even considerred putting the old sensor back. But finally I decided to do the wire splicing and crimping under car. The $1 wire crimper I bought from a dollar store gave me problem all the time. It was almost impossible to strip wires nicely under the car with a cheap tool. The job took me an hour, and the result is far from pretty. I wrapped each wire with a lot of 3M electric tape, then wrapped the whole thing with tons of tape to make sure it won't leak. I planned to stagger the connections and made it neat and clean before hand, but it ended up being a big lump :) Anyway it seemed to work. No code was thrown, and the engine ran smoothly.

The results after changing all the above? Well I couldn't tell. The engine seems to run smoothier at higher rpm and idles quieter. But I am not really sure it ran better although I believe it should :)

Some info that I have discovered these couple days, hope they might be helpful to someone:
a. the Bosch 13913 O2 sensor that everyone said works with our car, is for 1986 Ford Mustang V8.
b. Advanced Auto and NAPA has the flame trap for sale, part number is: Beck/Arnley 0460075.

I ended up not doing the strut rod bushing because I did not have a socket that will fit the rear bolt of the strut rod. Could anyone let me know what size it is; and what is the size of the bolt at the front? Oh and where is the connector of the O2 sensor and how can I access it? Thanks
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1994 944NA 100K miles