Mike if you were talking to me about the 4150 I went with this because of my experience with them (comfort zone) I realize the vacuum seconds can be more efficient but at the time I was not expecting the truck to be my daily driver for so long. I Have modified the carb internally for better street performance but I'm still working out the unknown kink in the timing curve before I can get the carb just right. Currently getting 14 city 17 hwy which is good for these as far as I can tell. Since my last 4150 years ago Holley kicked out the Street HP if I had done more research before my purchase I would have bought that instead for its tunability and the lack of choke. I'm kicking myself now.