Well I just did a few spirited runs very fast I might add. lol. Well came home pulled the plugs 2, 3, 4. Dark black/brown. Very nice. #1 Is dark black with hints of tan and white on the porcelin, and the tip is a normal looking silver. Is it normal for the first spark plug to always be leaner? I was thinking maybe this is where fuel cut off occurs when the car is shut off? The car has been tuned for the most part (still really rich) because we had to cut the session early because of slipping clutch. But the plug is always lighter. Any ideas?

 

it also seems like cyl 4 is richer than 3.. 3 richer than 2.. 1 = leanest.. by the color of the plugs. 4 is always darker and it goes down the line. Could this be because of the screwey endyn fuel pressure relief mod I did? My fuel pressure is like 38 at idle with vac line on. I have a aem fpr to put on so I guess I'll see if it helps at all.

 

fuel pressure relief mod?? what about your injectors? does the car seem to be running rich, or just your plugs are showing signs??

 

i've seen this happen when a healthy shot of nitrous is added

 

I think It as to do with the air coming in...... its the last one to suck up the leftovers.... and for fuel in the rail... its the same i think... the farther it is from the source.. the less pressure it has so a bit less fuel goes in........

Ive noticed that too.... when i checked my plugs.... #1 was a little whiter than the rest...

 

I think the Y8 intake manifold would help this, since all the air is drawn from almost the same point where as the A6/Z6 intakes look more likey to favor one cylinder.

The Buick guys have this problem with the rear two cylinders on there motors since air is effected by G-force just as everything else is. Were you by chance doing a doughnut in a clockwise circle ?? Hehehe..

Your only as strong as your weakest cylinder, so I'd tune off the #1 plug.

The fuel rail getting more presure on one side vs the other could also be doing it. The #6 cylinder on VR-4s is almost always the first cylinder to have trouble ( head gasket, burnt/cracked pistons, shot rings ) b/c the #6 injectors is dead last to get fuel and the fuel rails tapper in the middle ( they were recycled from the V6 motor used in older dodge mini-vans !!! ).

Or maybe you have one D16A1 piston and 3 normal pistons, but prob. one of the first two reasons...