Shares of Kinder Morgan Inc. slipped 0.2% in premarket trade Monday, after the oil and gas pipeline operator was downgraded at Stifel Nicolaus, citing concerns over valuation. Analyst Selman Akyol cut his rating to hold, after being at buy for more than three years. He kept his stock price target at $22, which is 7.2% above Friday's closing price; Stifel defines a hold rating as a total return of -5% to +10% over the next 12 months. The stock has soared 33.5% year to date, while the S&P 500 has gained 15%. Akyol said he continues to view Kinder Morgan favorably, given its more moderate leverage, high coverage and dividend growth, but he said the valuation already reflects the positive catalysts. Kinder Morgan's dividend yield at Friday's closing price was 4.87%, which was above the SPDR Energy Select Sector's payout of 3.39% and the S&P 500's implied yield of 1.99%, according to FactSet.