KDF, I had the same "stumble" at 70. Drove me crazy(r)!!! I went from a 76/31 (main/int) jet to a 78/33 and have not had the first stumble since. After posting that change, Ray told me that going to a larger intermediate may not always be the best thing. He said that increasing the main air bleed would have been his first choice. Still, I've had no problems since the change but I'm new to dogs and Ray is an Ole Timer Big Dog (border line on being euthanized for hip displasia). JK Ray! I would get more info on the long term affects of going to a bigger intermediate vrs going to a bigger main air bleed. Damn~! That was no help, was it?