If this is on your NBS, the one in your sig, you have 8 injectors (1 per cylinder). If the injector for cylinder 7 were either not functioning or functioning improperly could cause the code. P0307 is Powertrain Misfire Cylinder 7; P for powertrain, 0300 series is misfires, 01 through 08 denotes the cylinder (could be higher for more cylinders).
There should be nothing under your dash that would have any effect on your engines controls. The ECM is under the hood and the engine harness, control side of it anyway, is all under the hood. If you have access to a scanner, you could see if the injector is working. Lots of things you could check to see if it is working even without GM specific access from something like a Tech II. You could compare short term and long term fuel trim from one bank to the other, or oxygen sensor readings bank to bank.
I would bet money that it is an injector. The reason the engine doesn't shudder or shake or die with a dead injector is the other seven cylinders are keeping it going. Was your Intrigue a TBI? If you lost an injector on TBI, you'd be losing about half the fueling depending on the setup and the failure.
Anyway, hope that works. You could always pull the injector and see if you smell fuel.