Brian:

When you say a "Baffle" in the exhaust I'm assuming you mean it has a throttle butterfly in the exhaust that closes as the throttle is closed. This should be adjusted to be fully open at full throttle, and be closed just as the carb barrel closes. This is the initial setting - where you start.

You have to start adjustment at full throttle, I suspect you're still way lean. As you speed the engine up, when it starts to sag open the needle until it picks up again. Keep doing this (don't take it back to idle) until you get full rpm. From this point you can work on the idle, leaving the needle alone bring the rpm down gradually, you might disconnect the link to the exhaust throttle while you're doing this. As the rpm comes down you'll probably go rich. The exhaust valve is your low speed adjustment. Leaving it open is lean, closing it is rich.

Once you know pretty much where the exhaust has to be positioned at idle, work with the link from the carb to get it to follow the throttle as needed.

Have fun.

Bill.