The average price for a gallon of gas in Idaho has cleared the $3.50 mark, bringing Gem State pump prices closer to record highs reached in 2008.  AAA Idaho reports Idaho's pump price for regular-grade gas was $3.51, up three cents from last week but still 12 cents below the national average.  Lewiston reported the state's highest price at $3.60 and biggest increase, up 7 cents from last week, among the six cities surveyed. Idaho Falls checked in with the lowest price at $3.45.   AAA says some of the increase is due to the annual draw down of gas inventories as traders empty winter blend stocks to make way for a mandated switch to pricier summer blends. Idaho pump prices reached $3.75 per gallon in May 2008.