Ok.
Changed my ypipe.
CEL came on
Got a combo code 0304-knock/0303 front left 02 sensor.
0303 went away.
light went away.
0304 remains as ghost code.
I checked the impedence of the 02 sensor and it was .5ohms higher than
the specs in my Chilton's manual.
Cleaned it, still getting the 0304 ghost code.

My question is-is .5ohms enough to make my engine knock enough to
trigger the knock sensor?

 

Maybe you had 0304 before you installed the y-pipe?

 

yep, that's another possibility i thought of.
it would be a bit too coincidental though. honestly,
i'll probably get another 02 sensor anyway, but if it's
the knock, i'd want to spend the money there first.
if it was the knock, wouldn't it severely retard the timing?
i mean, it might be less powerful, but it feels fast.

 

If it's KS the most noticable power loss is under 3000rpm. If you like to step on it you may not notice the loss of power since you will be at or over 3000 most of the time.
Measure the resistance of the KS; AFAIK it should be 500-650 KOhm.

 

Stupid question time.
I'll need to remove the KS to test, right?
Will my car be able to function w/o the KS?
If I take it off, and it's bad, I'd rather wait
and put a good one on than put this bad one on, only
to swap it out again. I hear they're a *****...

 

No, no need to remove it.
Get a digital multimeter, unplug the KS connector, connect one multimeter probe to one of the pins on the harness that leads to the KS and the other probe to a ground on the engine (or negative on the battery). If you get an open circuit signal, try the other pin on the KS harness. (I think the pin that's closer to the front of the car is the one that should show resistance when measured)
And yes, the KS is a b**ch to replace but it's doable.