You changed a pretty big thing. The Airgap blocks off the exhaust cross over that heats the carburetor. This is why you've run into different drivability and also whi it runs better warmed up. Sounds like the carburetor needs to be richened up to compensate. It was probably on the verge of being too lean before the swap, the intake swap just pushed it over the edge. This should be easily overcome tuning on the carburetor......and for WAY less than 600 bucks. If you were close by, I would say bring the beer and I would hook you up.
