[jab]

I have a 427 FE Shelby aluminum block stroked to 482 and have not been able to get it to idle without popping and surging, and occasional popping with increased RPM, whether under load or not. The motor is in a Cobra with accel gen7 electronics and dual hi band O2 sensors with a custom IAC (Idle Air Control)plumbed into the rear of the manifold with 8 runners. The TWM stacks were synched using a synchrometer. It has a high lift Crane solid lifter roller cam with 10.5 pistons. We have tried everything and can't get it to run right. The MAP sensor is all over the scale and the latest diagnosis is that the stock plenum in the TWM manifold needs to be larger. This would mean installing an external plenum, as there is no room in the stock location. I don't know whether this is the right way to go, or another dead end. Has anyone had this problem?