if i'm still running all my egr stuff, will a breather cap screw anything up? also, what is the benefit from using one? i have heard good and bad things about them. can anyone enlighten me?
The good thing is that you'll be venting any excess crank case pressure without inadvertently putting oil into your throttle body.
The bad side is that your PCV system will no longer function like it's supposed to.
An alternative would be to isntall an air/oil separator into the line running from your filler cap to the throttle body (if oil in the intake is what you're attempting to cure).
Some might say that a breather cap allows unmetered air into the engine. Although that might be true, it's not enough to have any noticable effect on the EEC (The EEC IV is relatively dumb).
i'm having no problems, i just like how they look, and i've also heard they can (and heard the opposite) be better for your engine. if my car is running rich, would the addition of unmetered air actually make it run a little better? have one, but when when i downshift, i sometimes get a CEL for a sec, but it disappears right away when the rpms drop. i thought it was probably from my o2's being further back now, (b/c of LT's), but i dont get any codes for that. only codes i get with KOER is 94 (R), 44(R), and 33(R). 33 is EGR Valve not opening properly. 94 is from clutch not in (i think) and 44 is thermactor fault, but i removed it all. no codes with KOEO. could the breather cap be throwing a code? should i switch back to normal oil cap?
No... I don't believe that the breather will affect your fuel mixture or cause a code. It just doesn't make that much of a difference in terms of unmetered air with the A9X family of Ford ECUs. About the only thing you might notice is that your oil comes out a bit a darker during an oil change due to the PCV system not being allowed to operate optimally.
unmetered air is BAD but like he said its so small it wont make a difference.
if you have too much un metered air, like a big vacuum leak. it will run lean
heres a simple example.
the MAF is telling the computer how much air is passing thru the meter. and the computer takes this reading and shoots out the right amount of fuel for the air the MAF said was coming. if you have a vacuum leak, air is coming in after the MAF, that the computer doesnt know about it thinks its giving the right amount of fuel but there is actually more air. so it will run lean. of course there is alot more than goes into how much fuel the engine gets but this is a simple look at it.