I have been wrestling with this problem since I bumped fuel pressure. Thanks to RBob, Grumpy and JPrevost, we found out my BB injectors were going static at WOT at an AFR of 14:1. So we bumped FP from 10 to 16 and it make quite a difference. I am not sure this problem is related but that's the history. Once the motor gets to about 85c-90c, the idle will seesaw. In fact, its more like the motor is shutting down but the stall saver keeps it from doing that. Also when at light cruise or slight decline, I will have my foot on the accelerator very very lightly and the motor will stumble. There's no stumble at part throttle accel or WOT. It runs great. I have played with the bin but no difference. BTW, this is on an 84 Crossfire. The stumbling at idle is not sporadic like a vacuum leak. You can actually time it about every 8-10 secs.