Investec has lifted its recommendation for temporary power and temperature control group Aggreko from 'hold' to 'buy' following the company's strong 2012 results.Revenues rose 13% to £1,583bn in 2012, slightly ahead of Investec's £1,578m forecast, while pre-tax profit (PTP) increased by 11% to £365m, bang in line with estimates. "Aggreko has delivered on the FY12 numbers and is not changing its guidance for FY13," said analyst John Lawson. He said that while underlying forecasts will remain the same, Investec is likely to raise its 2013 PTP forecast by around £5.0m to £340m due to currency movements."There have also been some more encouraging signs in current trading year-to-date. On strategy, the group has reconfirmed its confidence in the business model and given clear financial guidance. Today's update is encouraging and we move to 'buy'," Lawson said.Investec's target price for the stock has been lifted from 1,750p to 1,940p.The market reacted well to the results on Thursday morning, with shares up a whopping 14.16% at 2,007p by 11:27.BC