Prudential is "firing on all cylinders", with its final results beating consensus expectations on all key performance measures, according to UBS."The Asian growth story remains very much intact, while super-normal US profits are likely to take longer than we previously thought to be competed away," says the broker.Its only concern is Asian persistency, but "management's optimism in this area is telling given their track record on assumption setting," according to UBS.The stock is yielding 3.5% prospectively which the broker says is undemanding given the group's structural growth potential.UBS remains a buyer and ups the target price from 800p to 850p, saying "our detailed analysis suggests a strong underlying picture."