What size injector?
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It will probably be smokey no matter what... The lag probably has more to do with size of the exhaust wheel than it does being under fueled. You could run a 250 if you want but those laggy spots at low rpm's will be worse and you may not be able to clear them up... Or just barely but if you go with a 7x.012 with lift they will be cleaner than say my 7x.014 due to smaller orifice, both are 250's but different companies rate them differently, just make sure you know the size of what you get