Proeagles, I don't know the specifics of the FAST system, but your base timing is an important number, as the ECU spark maps will add to the base value that's in their programming. My Edelbrock unit requires the timing to be set at 10 BTDC. Having it a few degrees later will just affect performance, but bumping your base timing more advanced could be more catastrophic if you're pushing the limits on total timing in the computer. It might not be convenient, but can you weld on a three bolt collector end plate, and a corresponding one on your exhaust for a gasketed, leak free joint at the collector? I don't like the idea of a slip joint there, given the proximity to the O2 sensor. Or better yet, fix the leak and move your O2 sensor down into the exhaust pipe as opposed to the collector?