I run the Edelbrock RPM intake; it doesn't have a heat cross over. It was into the 90s yesterday though. The motor is a low deck big block, currently at 470CI. I am really warming up to the idea of some sort of fuel pooling, and I appreciate the thought. The AFR swings don't occur at low RPM, nor at WOT regardless of RPM. It only seems to occur at a certain RPM range. Advancing the cam timing looks to be in my future; hopefully that will help.

Yesterday I tinkered some with the carb using a thought from Y07_A66. I dropped the main jet down significantly (to 69s). To my surprise, this really leaned out the low RPM range, even causing a lean miss from off idle and up. I switched in my biggest IFR (.036) and it was still lean. Then I dropped the IAB from .070 to .065 (the smallest I have), and it improved some to the point where the car was just driveable, but still way too lean (16-17 AFR). Never had this problem before! So, now I am going to need to buy some bigger IFRs. I didn't want to drive it much, given the AFR, and didn't get a chance to take it far enough to try highway speed.