Help identifying these electrical parts / connections under the hood?

[nanotech9]

So, after owning my car for nearly 10 years, i've never asked what are some "odd" stuff i have hanging out under the hood...

'91 318is

First up, the easy stuff...  Hiding under the plastic cover on the firewall just to the rear of the engine...





Now for the hard one...   the part numbers don't seem to shed much light.

This connector was installed on the car when i bought it back in '01... car had 120k on it back then, came out of texas.

Its basically a short extension to the plug from the harness to the AFM.  I never noticed a difference in having it installed or not, so i unplugged it YEARS ago and just looped it back into itself and zip-tied it in place (to keep from loosing it).

There is definitely some small square *something* hiding inside the long rubber boot with the numbers on it.... haven't tried to pry it apart.  I'm wondering if it was a mod like we do to the BMW motorcycles where we add a resistor inline with the air temp sensor to make the ECU think its colder out and add 6 - 10% more fuel...?  (just a guess?)

Numbers are:
1 284 463 500
1 734 516 . 3

Any ideas?

[DesktopDave]

The first plug is to enable the AFM CO potentiometer in markets with no catalytic converter, like the older LH Jetronics require.  We've determined that it must NOT be connected if you have a cat.

The second item is exactly as you've guessed...a resistor pack to improve the idle & low speed stumble as a rolling TSB, IIRC.  It dampens the voltage spikes off the AFM.  I pulled mine out as well...water was collecting in it, throwing a 1915 code & keeping the motor from running properly.

[nanotech9]

cool... i love blindly guessing and being in the ballpark!

talk to me about the first plug... lets pretend we're in a state w/o inspections (because we are) and lets pretend this is a purely track car, and it has no cat (for like 8 years now).

Is there any info around here on connecting it and its effects?  (no i haven't searched yet, I know i've got the cart before the horse here...)   If not, no biggie..

[DesktopDave]

If you have an AFM with the CO circuit I'd figure you could pick up a few HP with a wideband, some sensible timing & EGR...just like tuning the old analog LH Jet system.  I don't know specifics...but it's definitely been done.