You know that sounds like some gas is seaping in somehow. That would expain it, Right after you stop and then start it thats not enough time for the gas to drip in. After a 1 hour or more the gas goes away and or the motor likes that little bit of gas cuase its getting cold. But after 15 mins its like flooded. Bet that it it, but I am a Holley guy so I would call Eddy tech and ask them. Could be your float is too high, but I would call them, think its a toll free #