I am very happy with mine, I get decent milage and my truck starts every time with just a few seconds (I can get it to start more quickly by turning the mixture screws a quarter of a turn but I like to give the oil time to start circulating) of cranking on the coldest of days. And, it flows 750 cfm, not 650. There are only 2 qjet sizes I am aware of and they are 750 and 850 cfm.