I own a 96 slt 4x4 K&N 3. 54 rear Reg. cab Auto Trans. 255/85/16S,I'm getting about 18 m. p. g. ave. (no towing). 60% Hwy. 40% City. I'm thinking about coming over to the dark side and owning a 24 valver. But the 12 valvers are scaring me with their M. P. G. claims!, with normal driving isn't...