I doubt evap has anything to do with it. The IACV is the sensor that has 2 hoses right behind the intake manifold....... the screen on those usually gets dirty and causes it to idle all weird......

the one behind the throttle body is the TPS sensor, that could be a reason why it also slows down, but that sensor does not affect the idling of the car.

Did you happen to mess with that sensor when you are doing the swap ? If so, then the voltage on the TPS is all out of wack. I can tell you how to adjust it but I need to know if you played with it...