I'm continuing to experience rough idling with the M-37. It seems to occur after the M-37 has been driven for about 20 miles. The last time it happened was driving home from a car show.. The M will run rough if I don't keep it at a fast idle. I've replaced the needle and seat. There are air bubbles occasionally between the fuel pump and air filter. The last incident happened late in the afternoon and it was not a excessively hot day. This same issue happened at the rally too. I'm thinking it's more than vapor lock.