RBC Capital Markets has upgraded its rating for Intertek from 'underperform' to 'sector perform', providing a boost to the quality control and testing group's stock on Tuesday morning."After significant recent underperformance, we upgrade to 'sector perform'," RBC said. The stock has underperformed the market and the sector by 14% and 19% so far this year, respectively, and while the valuation is still not cheap it is trading at a 10% discount to the testing segment, the broker pointed out.Nevertheless, it still trades at a premium to the services sector though RBC thinks this is warranted given its growth, quality and M&A potential.After cutting its earnings forecasts post first-half results to reflect slightly lower growth and weaker margin assumptions, the broker said: "we believe forecasts now look achievable, with the typically cautious management team appearing more confident on second half margin stability and improvement into 2014.""We like the testing structural growth story, comps are now more benign and we see a pick-up in M&A as likely. Whilst valuation is still full, we now see limited downside risk."The target price has been raised from 2,850p to 3,050p.The stock was trading 3.27% higher at 3,186p by 10:18 on Tuesday.BC