Its Running Rich Bad! Advise Please

1. Pull the codes.
2. Remove the vacuum hose from the fuel pressure regulator. If it is wet with gas, you may have a leaky diaphragm and it's spitting fuel into your upper intake.

There is little reason to run "race" gas unless you've got a high compression engine or are running a ton of boost. Not only that, these fuels burn too slowly in a nearly stock engine, and may actually cost you power and create carbon build-up in the engine. Depending upon what additives are in that "race" gas, it may have damaged the O2 sensors.

It could be a MAF or O2 sensor issue. However, could also be a ECT, ACT, and/or MAP voltage issue. That said, if something is really out of spec, a code should have been thrown. Since you ran the codes and nothing popped up...no codes at all...like a open ground issue...or it performed the KOER just fine and no codes?

It could be just old race gas left in the tank. Maybe it just isn't burning completely. Have you tried emptying the tank and replacing it with some new fuel? I know my car runs a little rough in the Spring, even with fuel preservative in the tank. I have to run her down to empty and get new fuel in it before I can really do any tuning. Maybe it's just as simple as that.

Do the plugs look carbon fouled or just clean/wet?

Any other work done on the car recently?

Has the ECU been recalibrated for the nitrous...two stage chip...one for naturally aspirated, one for nitrous?

This Cobra computer is combined with a MAF calibrated for 19# injectors and you are running 24# injectors...like stock, correct? Something totally different?

If none of these seem to be an issue, I'm going to direct you over to my friends at www.stangtuning.com Real racers with a lot more experience than I have.